Some eurypterids from the English Coal Measures

352 SOME

EURYPTERIDS FROM THE COAL MEASURES.

ENGLISH

By L. R. MOORE, B.Se. [Reteived 26th March, 1936.] [Read 5th June, 1936.]

AN impression

INTRODUCTION.

of Eurypterus collected from fallen material in a disused roadway on the NO.3 seam of Bromley Colliery near Bristol, was given to the writer by Mr. J. Smith, Manager of the Pensford and Bromley Collieries. An opportunity to revisit. this locality occurred some months later, and the writer was fortunate to discover the actual specimen in situ. The specimen which had been preserved upside down was found exposed, adhering by a very thin layer of shale to the main clift roof. The fragmentary nature of the soft shale rendered it impossible to obtain the specimen without breaking it. However, each fragment was collected and since pieced together. Further dissection and mounting shows the specimen to be exceptionally well-preserved, and the most completely known Eurypterus from the Upper Coal Measures of Britain. Of the three species of Eurypterus which have been described from the British Coal Measures, namely, Eurypterus moyseyi, E. derbiensis H. Woodward (r907) and Eurypterus wilsoni H. Woodward (r888) this specimen most closely resembles the latter. The two former species occur at a horizon at the base of the Similis-Pulchra zone of Derbyshire, whilst the holotype of E. wilsoni was collected from the Upper Coal Measures of the Somerset Coalfield, the species being known by its mesosoma only. No other example of this species appears to have been recorded, but an undescribed example showing four mesosomal and four metasomal segments in the Bristol Museum adds to our knowledge of the species. A small prosoma also from Somerset, in the Geological Survey Collection, may also belong to E. wilsoni. The Bromley specimen here described may not be quite identical with this species, but it is probably closely related to it. In the course of this investigation Dr. J. Pringle kindly called my attention to a specimen of E. moyseyi in the Geological Survey Museum, from Ilkeston, Derbyshire, which shows important details not described in the types. Other specimens of Eurypterus have also been examined in the collections of the British Museum (Natural History), and in the Bristol Museum and Art Gallery by the kind permission of Dr. W. D. Lang, F.R.S., and Dr. F. S. Wallis.

EURYPTERIDS FROM ENGLISH COAL MEASURES.

353

I wish to thank Dr. J. Pringle for the great interest he has shown in this work. To Professor A. E. Trueman I am greatly indebted for his valuable help, and guidance throughout the preparation of the paper. I wish also to acknowledge assistance from the Colston Research Fund of Bristol University in defraying some expenses of this investigation. EURYPTERUS WILSONI H. WOODWARD. Before describing the Bromley specimen it will be useful to record such new information concerning E. wilsoni as is made available by the two unrecorded specimens already referred to. The specimen in the Bristol Museum and Art Gallery, No. Ca7193, was collected by Mr. T. Fry from the Camerton Colliery, Somerset, where coals of the Radstock Series of the Upper Coal Measures are worked. It consists of eight extremely well-preserved segments, representing the actual dorsal surface of the creature, and lies upon a blue shale containing plant remains, in the form of a Lepidodendron and a pinnule of Neuropieris, which, however, are only visible on the back of the slab of shale. Dimensions : SEGMENTS OF MESOSOMA.

No. of segment. 3rd. 4th. 5th. 6th.

Length (ant-post.) Max. width (along post border). 8 mm. 48 mm. 7 mm (approx.) 47 mm. 46 mm. 7.5 mm. 6 mm. 43 mm.

SEGMENTS OF :i\IETASOMA.

rst. znd. 3rd. 4th.

6.5 mm. 9 mm. 10 mm. 9 mm.

38 29 25 18

mm. mm. mm. (approx.) mm.

The first and second mesosomal segments are missing from the specimen, but the mesosoma as seen presents a rectangular outline with a tumid appearance, its segments being sharply differentiated by slightly arched anterior and posterior borders. The posterior angles of the segments are slightly more acute than those seen in the type of E. wilsoni. An important feature is provided by the preservation of the first metasomal segment (not represented in the holotype), which possesses straight lateral margins about 13 mm. long, produced backwards and slightly outwards. The ends of the posterior margin of this segment are curved sharply backwards to meet the lateral margins in a sharply pointed spine. The remaining metasomal segments are distinctly longer than those of the mesosoma, and have a transverse median depression, whilst their anterior and posterior borders are

354

L. R. MOORE,

inflated. The lateral borders of the second metasomal segment are well-preserved, and bear powerful sharp spines about 6 mm. long, which are directed backwards, and outwards. A similar spine is visible to the right hand of the third metasomal segment. The spines of the metasoma have a strong central ridge running from this point, and dying out in the ornamentation of the segment. Several fainter striae occur on either side of this. The anterior portions of both mesosomal and metasomal segments are covered with minute squamae, which rapidly develop in the posterior half of the segment only, into stronger

FIG. sS.-Eurypterus wilsoni Woodward X

It.

broadly triangular squamae, their apices including angles approaching 90 degrees. Oblique striae are well developed on the lateral margins of the mesosomal segments, and are seen to be due to the alignment of the squamae, one border of which becomes elongated. Evidence of the median appendage of this specimen is present in the form of rounded raised areas on the first three mesosomal segments preserved. Those segments which are common to this specimen and to the holotype of E. wilsoni are almost identical, and its

EURYPTERIDS FROM ENGLISH COAL MEASURES.

355

occurrence at a corresponding horizon supports its reference to that species. The holotype of E. wilsoni H. Woodward (r888, p. 420) was obtained at Ludlow's Colliery, Radstock, Somerset, from the Upper Coal Measures. The actual horizon is doubtful, but was probably in the Radstock Series, although the upper part of the underlying Farrington Series had also been explored at that time. E. wilsoni is therefore the youngest known British species of Eurypterus. Another Eurypterus, found by Dr. R. Kidston in r877 at Radstock and now in the Geological Survey Collection (No. 49452), is also provisionally referred to this species. It was likewise found in the Radstock Series of the Upper Coal Measures. The compact dark blue shale upon which the specimen is preserved contains plant fragments, a good specimen of Alethopteris grandini Brongt being present. Unfortunately only the dorsal surface of the prosoma is present, a large part of the posterior border being absent. At one point beneath the head shield and near the left-hand eye occurs what may be a shell. Dimensions : PROSOMA.

Length, anterior to posterior Maximum width of posterior border Width of prosoma across eyes Distance apart of eyes 'Width of eyes Length of eyes

16.0

mm. preserved

23.0 mm. (approx.)

18.5 mm. 7.5 mm. 1.5 mm. 3.0 mm.

The anterior border of the prosoma is broadly rounded, and centrally shows a slight notch in its outline. The lateral margins are almost straight and inclined, passing with a pronounced curve into the anterior border at a point some 3 mm. in front of the eyes. A channel extends round the front of the head shield with a maximum width centrally of 1.5 mm., at which point it is interrupted by a slight triangular furrow. The right-hand genal angle is almost complete, being acute, and probably extending slightly backwards as a spine. The eyes are small but prominent, reniform in shape, and situated slightly nearer the lateral than the anterior margin; their posterior borders lie nearly midway. between the anterior and posterior margins of the prosoma. Median ocelli are not visible though a small area behind the eyes, devoid of normal ornamentation, may have contained them. The ornamentation consists of very fine crescentic scalelike markings irregularly distributed, which develop posteriorly into a few broadly triangular squamae. This specimen in its proportions and shape resembles E. imhofi Reuss. (r855, p. 8r, pl. III), a specimen obtained from the Pilsen Coalfield of Bohemia, and from a horizon considered by Stainer

356

L. R. MOORE,

(1915, p. 644) to have been at the junction of Carboniferous and Permian. EURYPTERUS CF. WILSONI H. WOODWARD. The Bromley specimen is associated with many plant remains including Neuropteris, Cordaites and Lepidophyllum in a very soft thinly bedded shale occurring about three feet above the NO.3 seam. The seams above and below ha ve yielded specimens of freshwater lamellibranchs of the genus Anthraconauta which indicate a horizon within the Phillipsi zone. The specimen now in the British Museum (Natural History) (No. In. 35610) shows the actual dorsal surface of the prosoma, mesosoma, and possibly five metasomal segments. A portion of a further segment considered to be part of the ultimate metasomal segment is represented by an impression, whilst the greater portion of the actual proximal end of the telson is preserved. The lateral margins of the prosoma, and of the third and fourth mesosomal segments are missing from the left-hand side of the specimen. The impression now presented to the Bristol Museum and Art Gallery (No. Cbz55z) shows a complete dorsal surface of the prosoma and mesosoma, with the first and portions of the second and third metasomal segments. The dimensions given are taken from both the specimen and the impressions. Width of prosoma across eyes Distance apart of eyes Width of prosoma at posterior margins .. Length of prosorna (anterior-posterior) ..

32 mm. 12 mm. 42 mm. 28 mm.

SEGMENTS OF MESOSOMA.

No. of Segment.

rst, znd, 3rd. 4th. 5th. 6th.

Length (ant.-post.) 3.0 mm. 6.5 mm. 8.5 mm. 7.0 mm. 6.5 mrn. 6.0 mm.

Max. width along post border. 41 mm. 46 mm, 48 mm. 47.5 mm. 45 mm. 42 mm.

SEGMENTS OF METASOlllA.

rst. 7.5 mm. 39 mm. approx. znd. 7.5 mm, unknown. 3rd. 9 mm. 23 mm. 4th. 12 mm. 22 mm. 5th. 13.5 mm. 19 mm. Supposed part of ultimate metasomal segment. 6th. 5 mm. approx. 6 mrn. approx. TELSON.

Length preserved .. Width at proximal end .. Minimum width distal end

30 mm. 6 mm. 1.5 mm.

Prosoma. The prosoma has been slightly crushed, but is considerably broader than long, and possesses an anterior border which is nearly straight in appearance, with probably a slight median concavity. The antero-lateral regions are sharply

EURYPTERIDS FROM ENGLISH COAL MEASURES.

357

rounded without angularity, whilst the lateral margins remain curved to within a distance of 10 mm. from the posterior border, from whence they become straighter. The posterior border is generally straight, and the shape of the prosoma may be described as rather elongate trapezoidal. The genal angles are poorly seen, but appear to include an angle of roughly 90 degrees.

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59.-Eurypterus cf. tuilsoni Woodward.

The eyes are reniform in shape, elongate, and widely separated, being 5 to 6 mm. long, and 2.5 rnm. wide, their compound nature being visible in the right eye of the specimen. They are so situated that their posterior borders lie midway between front and back of the prosorna, whilst their anterior ends are equidistant (8 mm.) from both anterior and lateral margins. One of the paired median ocelli is visible in the centre of the

358

L. R . MOORE,

prosoma and takes th e form of a rounded ringed prominence', the ot her has broken away lea ving a shallow pit. The pro soma is devoid of sha rp features, and owing to the irre gular surface on which the specimen is preserved it is somewhat difficult to distingui sh with cert ainty bet ween accidental and original markings. An almost circular elevated area occupies the anterior portion, including both the eyes and the ocelli, its posterior margin extending behind the median ocelli. The highest part of this slightly elevat ed area occurs immediately in

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front of the eyes, a ridge possibly divided by a median depression appearing to run acro ss between their anterior borders. The posterior border of the prosoma is gently eleva ted, giving rise from its median point to two further elevated ridges running ante ro-lat erally to beh ind the eyes, and separat ed from the central elevation by a marked depression. Th e deepest depressions on the pro soma occur behind the median ocelli and immediately in front of the mid-point of the eleva te d post erior border. They consist of two rather oval-sha ped depr essions sepa ra te d by a slight rid ge, and may be relat ed t o

EURYPTERIDS FROM ENGLISH COAL MEASURES.

359

muscle spots as described by Clarke and Ruedemann (1912, vol. I, p. 27). A flattened area with its maximum width of 6 mm. in the region of the eyes extends around the prosoma as a rim, the observed features of the prosoma merging into it. Prosomal appendages. From under the left hand genal angle of the positive specimen appear three joints which extend under the lateral margins of the first and second mesosomal segments. Their position and size would indicate them to belong to the ectognath or so-called swimming appendage. To the left of this appendage three rather elongated joints occur, which can be traced to join a portion of a joint extending from the broken margin of the prosoma. A further small fragment to the left of these exhibits the articulation of two joints with a final termination in what may be a pointed dactylus. M esosoma. The outline of the mesosoma is sub-rectangular, though the lateral margins are slightly convex, providing a maximum width at the third and fourth segments. The specimen shows some degree of overlapping of its segments, suggesting that these were not fully extended when preserved, whilst the second, third and fourth segments have been crushed and broken centrally. A feature common to many eurypterids is seen in the extremely short first segment, the lateral margins of which are distinct, being, almost completely rounded, whilst the posterior border extends slightly beyond the anterior border. On the lefthand side of the impression, and the corresponding side of the actual specimen, the rounded antero-lateral borders of the second, third and fourth segments are clearly seen, whilst their lateral borders become progressively straighter and extend backwards to meet the posterior borders of the segments in almost a right angle. The posterior angles of the fourth segment are however, more acute than those of the preceding segments. The second segment shows some overlap posteriorly on to the third segment, but except near the margins of the mesosoma the posterior border of this segment has been destroyed, so exposing to view a greater area of the succeeding segment. This feature is only well seen on the actual specimen. The fifth and sixth segments, the lateral margins of which are only well seen on the impression, agree in many respects, having very slightly arched anterior and posterior margins. The posterior margins extend some 2 mm. beyond the succeeding segment, being in this projecting portion turned posteriorly to meet the straight lateral edge in an angular projection. This latter feature is more strongly produced on the sixth segment. The seventh, or first rnetasomal segment differs only slightly in its proportions from the preceding segments, showing similar arched anterior and posterior margins. The anterolateral regions are sharply angular, the lateral margins being PROC.

GEOL. Assoc., VOL. XLVII.. PART 4. 1936.

23

L. R. MOORE ,

straight and extending backwards and outwards, with a length of 9 mm. meeting the extended curved post erior border in an acutely angular proj ection having the semblance of a spine . The last three segments are strongly tumid centrally, but have flattened lateral margins which are separated from the central portion by oblique lines running from the posterior lateral angles. It is possible that these lines, and the tumidity of the latter segments, were produced by crushing. Segments of metasoma. Two of these segments are beautifully pre served, but between these a nd the first metasomal segment the specimen has been broken, and it is somewhat uncertain whether one or two segments are present. It is more probable that there are two, making five metasomal segments in the sp ecimen . This interpretation is supported by the fact that on what is presumed to be the second metasomal segment the ornamentation, though incompletely preserved, shows coarser squamae near the posterior border comparable with those on the posterior parts of each subsequent segment. The post erior border of the second segment is thus considered to occur along the ridge slightly in front of th e fracture traversing the anterior border of the third metasomal segment . The posterior border of the third segment is straight and strongly inflated and bears a strong spine on it s right-hand side. The remaining two segments are very similar. In th e fourth metasomal segment th e ante rior a nd posterior borders are slightly arched a nd inflated , whilst a transverse depression occurs rather nearer its ante rior border. These features ar e similarly seen on the fifth segment. The two latter segments are slightly turned to one side , so exposing on their left-hand sides portions of their articulating surfaces, whilst the lateral margins of th e segments ar e gently rounded and sinuous, conforming to the observed dor sal features. Posteriorly, howe ver , the last two segments show flattened ex tensions from about the mid point of their lateral borders. These winged areas are directed backwards and outwards, and are produced into sharp spines extending beyond the posterior border of th e segments. The features sh own on the last two metasomal segments are similar to those seen on the Bristol Museum specimen of E. wilsoni . A further portion of the metasoma, considered to be part of the ultimate segment, is seen as an impression on a piece of shale to the right of the specimen, this segment was entire when seen in sift! (its outline is thus giv en), but was unfortunately broken in extracting it underground. Its posterior border is thought to fit on to the proximal end of the telson. Telson. The proximal end of the telson shows a width of 6 mm., but rapidly tapers with rather straight edges until it is 2 .25 mm. wide at a distance of 10 mm. from it s proximal end. A cent ral triangular ridg e tapers to form a broadly rounded

EURYPTERIDS FROM ENGLISH COAL MEASURES.

36r

carina which runs down the centre of the teIson, and is bordered on each side by a very sharp depression. The edges of the telson are smooth and appear flattened, giving the appearance of a flange. Clarke and Ruedemann (1912, vol. 1, p. 24) give a similar structure to this described, as being typical of the ventral surface of the telson, the dorsal surface being smooth. Though a length of 30 mm. of the telson is preserved, it is possible that it was even longer; the minimum width measured of I.5 mm. suggests that its length could not have been very greatly in excess of that observed.

3·

Ornamentation. This is generally well developed on the elevated areas of the actual specimen, and consists of either broadly triangular or crescentic squamae, varying in size, and where strongly developed, apparently overlapping marginally. Along the posterior border of the prosoma the ornamentation is fine, but well seen, and follows the two elevated areas running antero-laterally ; it dies out in a broad area of fine marking behind the eyes. Two parallel lines rising from this elevated area run anteriorly on either side of the median ocelli, past the eyes, and converge towards the ridge running between the eyes where they are marked by some rather coarser squamae. The actual

L. R. MOORE,

surface has in most cases been broken away from the flattened marginal area, but where it is preserved the ornamentation consists of very minute scale-like markings which often become oriented in such a manner as to give an appearance of anteroposterior striae. The prosomal appendages are strongly and uniformly ornamented by narrow triangular overlapping squamae, which give an appearance of small spines. The mesosoma is provided with sharp ridges bordering the

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segments, and whilst the anterior and antero-lateral borders have only minute markings, the ornamentation rapidly becomes coarser posteriorly, and is exceptionally well developed centrally in the second, third and fourth segments as shown in Fig. or. The stronger ornamentation assumes a broadly triangular appearance. All the segments show similar ornamentation. An oblique orientation of the squamae near the lateral margins produces a striated appearance, well seen in the posterior angles of the second and succeeding segments. This striation runs

EURYPTERIDS FROM ENGLISH COAL MEASURES.

363

into the apex of the angular projections described, giving them a characteristic appearance. The ornamentation of the metasomal segments is developed coarsely at their posterior end where it is seen to form very broadly triangular squamae shown in Fig. 62; in some cases the triangular form is lost and the largest ornamentation somewhat resembles small tubercles. A similar but stronger oblique orientation of the lateral squamae is seen, which produces eventually strong striations extending to the tip of the metasomal spines. The proximal end of the telson is likewise ornamented by fine triangular squamae which on the carina become elongated and spine-like. The actual surface of the telson is not preserved at its distal end. Evidence of the median appendage is present in the form of pronounced circular raised areas in the second and third segments, and it is around these areas that the ornamentation is most complex and strongly developed. The fifth segment shows a similar raised area centrally, but the extent of the posterior prolongation of the median appendage is doubtful. An unrecognisable portion of the creature lies to the right of the sixth segment of the impression, showing minute ornamentation identical with that described.

COMPARISON WITH OTHER SPECIES. The specimen under description very closely resembles E. wilsoni H. Woodward (1888, p. 420). The holotype of that species now in the collection of the British Museum, consists of the actual carapace showing the six mesosomal segments only, which are however, perfectly preserved, and do not exhibit any signs of crushing. The specimen designated E. cf. wilsoni is shorter in proportion than the holotype, but to some extent at least, this difference may be due to crushing or to the overlapping of the segments. The ornamentation is similar in form and distribution, both specimens showing also similar evidence of the median appendage. Further similarity is provided between the Bromley specimen and the Camerton specimen of E. wilsoni by the preservation of the metasomal segments, which differ only in that the spines of E. wilsoni appear to be larger and directed more strongly outwards. Woodward (1888, p. 421) stated that E. wilsoni would probably prove to be near E. mansfieldi C. E. Hall 1877 (see also ]. Hall, 1884), the scale markings of which he regarded as identical. Clarke and Ruedemann's more recent figure of the ornamentation of E. mansfieldi (1912, vol. I, fig. 47), however, shows this to consist of narrow closely packed scales, almost resembling spines. The lateral spines on the anterior segments

L. R. MOORE,

of E . mansfieldi are very strong , being forcibly directed outwards and backwards, but although such spines are absent in E . wilsoni they may have been broken off before preservation, for the spines on the metasomal segme nts of the Camerton specimen, here referred to E. wilsoni , are similar to those seen on the metasoma of Ii. mansfieldi. The prosoma of E. mansfieldi has a rounded anterior margin, and appears to taper more sharply than that in the specimens which are here designated E. d. wilsoni . The eyes of E . mansfieldi are widely separated, as in E. d. wilsoni , but whil st in the latter they are equidistant from both anterior and lateral margins, in E. mansfieldi they are almost tw ice as far from t he ante rior as from the lateral margin s. The areas of orn amentat ion of th e t wo species under discussion show some simil arity. It would appear therefor e th at whilst E . wilsoni and E. mansfi eldi show important differences warranting two separate specie s, these species as Woodward suggeste d mu st be regarded as closely related. Meek and Worthen's Eurypterus (Anthraconectes) mazonensis 1868[1]* (see also 1868[2]) differs in that the pro soma shows a prominent anterior concavity, whil st the lateral margin s are sinuous, with a swollen gena l angle which extends backwards as far as the second m esosomal segmen t . E. moyseyi H. Woodward (1907, pI. xiii, figs. 1, 2). . The holotyp e of th is spec ies, in th e Geologica l Survey Collecti on (Nos. 30192-30193). was obtained from the Shipley clay pit, Ilkeston, Derbyshire, at a horizon a few feet below the Top Hard Coal, and is contained in tw o parts of a single ironstone nodule. Woodward also figured another spec imen from the same locality. He mad e little reference in his description to th e counterparts of the tw o spec imens. The nodule containing the holotype was br oken along a plane following the dorsal surface, and whil st th e figured spec imen has lost the portion of the dorsal surface which covers the met astoma and gnathobases, to gether with the first and part of th e second mesosomal segments , the counte rpart shows an impression of th a t portion of the dorsal surface. Woodward's figure of the holotyp e is not altoge ther sa tisfac tory. It may be noted th at the right hand side of the specimen is obviously broken away, as also are the lateral margin s of the sixth mesosomal and first metasomal segments seen to the left of the specimen. In shape the meso soma is sub-rectangular, and less globose than the figure suggests, whilst the mesosomal segments are nearly straight , and do not show the abrupt arching suggested by fig. 1. The counterpart of this nodule (specimen No . 30193), from which the anterior portion of the prosoma has • For references see pages 374-5.

EURYPTERIDS FROM ENGLISH COAL MEASURES.

365

been broken away, shows the dorsal surface of the prosoma to have had a straight posterior margin ending in acutely rounded genal angles, which were not produced backwards as spines. The mesosoma, which is sub-rectangular in shape, shows six complete segments. Portions of the actual dorsal surface obscure the ends of the segments, but the first metasomal segment to the right of the specimen is clearly seen to be produced backwards into a spine. This feature is better seen on the second metasomal segment, which shows a straight lateral border meeting the backwardly curved posterior border in a spine-like projection. Additional information regarding the median appendage is obtained from the counterpart. It commences at the anterior border of the second segment, with an included angle of about 60 degrees. A maximum width is reached of 3.5 mm. along the posterior border of the second segment. From this point the appendage tapers, to end in a blunt point at the anterior border of the fifth segment. The other figured specimen (Fig. 2, No. 30194 of the Geological Survey Collection) is contained in an ironstone nodule which also has broken along a plane more or less following the dorsal surface; the counterpart of the nodule (specimen No. 30195) is essentially an impression of the dorsal surface, but shows attached portions of the actual carapace. Woodward's fig. 2 is a good representation of the features seen in the specimen, except in the region occupied by the opercular plate. Here, by reason of the partial removal of the dorsal surface, the ventral surface is exposed to view. The median appendage in this area shows important features not very fully interpreted by Woodward. Commencing at the anterior border of the opercular plate with an included angle approaching 90 degrees, the median appendage quickly reaches a maximum width of 3.5 mm. From this point it tapers gently in a posterior direction. The total length of the appendage preserved is 5 mm., but its appearance suggests a greater length. On either side of the tapering posterior portion of the median appendage is developed a spatulate plate with a maximum width of 2 mm. The anterior margins of these plates fit into the angles formed by the anterior and posterior portions of the median appendage. Posteriorly the spatulate plates and median appendage are covered by portions of the dorsal surface. The counterpart of this specimen, No. 30195. shows an almost complete impression of the dorsal surface of the prosoma, together with seven further segments. Faint evidence of the median appendage is seen extending into the fourth segment. Woodward's figs. I and 2, scarcely seem to represent the same species, but a comparison of the specimens indicates that only one species is present, since the arching of the segments in the figure of the holotype is greatly exaggerated, and the

366

L. R. MOORE,

supposed differences in the median appendages commented on by Woodward, are not very well established, owing to the incompleteness of the specimens. A further example of E. moyseyi from the same horizon and locality, and preserved in a similar ironstone nodule, helps in the interpretation of this species and calls for separate description. Comprising specimens No. 30249 and 30250 from the collection of the Geological Survey, this example is more completely preserved than either of the figured specimens. This remarkable specimen of Eurypterus is contained within a single ironstone nodule, broken along a plane which near the anterior end of the specimen has passed between the ventral and dorsal surfaces, and posteriorly, from about the third mesosomal segment, has followed the dorsal surface of the fossil. The larger part of the nodule (specimen No. 30250) thus contains a wellpreserved impression of the whole of the dorsal surface, whilst the counterpart (No. 30249) only shows the actual dorsal surface from the third mesosomal segment to the posterior extremity, the remainder having broken away, exposing the ventral surface of the prosoma and opercular plate. Dimensions :-Specimen No. 30250. Width of prosoma across the eyes Distance apart of the eyes Width of prosoma at posterior margin Length of prosoma (anterior to posterior borders) ..

22 10

27

mm. mm. mm.

19 mrn.

SEGMENTS OF MESOSOMA.

No. of segments. 1St. znd, 3rd. 4th. 5t h . 6th.

Length 2.5 3.5 4 5 4 3.5

(ant.-post.) Max. width at posterior border. mm. 27 mm. 28 mrn, mm. 29 mm. mm. 27 mm. (approx.) mm. 28 mm. mm. } h d mrn. crus e 26 mm.

SEGMENT OF METASOMA.

1St.

4 mm.

25 mm,

The dorsal surface of the prosoma is remarkably well preserved in specimen No. 30250, showing an outline with broadly rounded and somewhat flattened anterior border along which a narrow centrally notched rim is developed. The anterior border passes with a strong curve into the anterolateral border without exhibiting angularity. This curve persists to within the region of the eyes, at which point it passes into the almost straight, slightly inclined lateral margins. In general form the prosoma is somewhat elongate trapezoidal. The genal angles, though incompletely preserved, appear to be acute, and probably did not extend backwards as spines. A pair of median ocelli is distinctly visible, occupying a position in the centre of the head shield. The eyes are large and

EURYPTERIDS FROM E NGLISH COAL MEASURES.

367

prominent, reniform in shape, and widely separated , having a well developed ocula r node. Their posterior borders are slightly in fron t of the median ocelli, whilst they are approximately equidistant from both lateral and anterior margins of the prosoma. A broad depression (representing in the positi ve a slight eleva tion), commencing behind the median ocelli, runs between the eyes, here attaining it s maximum depth, to the ante rior margin, where it rapi dly sha llows an d is flanked by prominent rid ges representing acute cha nnels on the positi ve. These

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FIG. 63.-Eurypterus moyseyi. W oodward X ii.

rid ges ex te nd int o the an terior border. Behind the eyes the course of these ridges runs par allel with the lateral margin until a bout 4 mm. from the post erior border, at which point they turn sha rply into the gen al ang le, providing between this course and the m argin, a relatively smoot h a nd flattened area. A sha llow depression runs laterally in front of the posterior border, from the median point of which tw o sha llow depressions extend to behind the eyes. This pr ovides a sub-central triangular raised area behind the median ocelli, with it s apex posteriorly direct ed. Ornamentat ion is well deve loped along the post erior and a ntero-lateral depressions, in the form of overla pping, broadly

368

L. R. MOORE,

triangular or crescentic squamae. These are arranged in curving lines around the apex of the triangular area. This area behind the ocelli is less strongly ornamented, whilst the flattened areas, except for occasional lateral oblique striae, appear smooth. The prosoma of specimen No. 30249, showing the ventral surface, is most important. Its outline is broken particularly to the left, whilst the preservation of prosomal appendages has tended to make it incomplete. The anterior border, however, shows the same broadly curved outline, with a A

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-:

FIG. 64.-Eurypterus moyseyi, Woodward X j.

median channel corresponding to the notch observed on the impression No. 30250. In the centre of the prosoma occurs the metastoma, or post-oral plate, the base of which is concealed. This organ, the anterior portion of which is placed 6 mm. from the front of the prosoma, and is 5 mm. wide, extends posteriorly for a distance of 9.5 mm., with its greatest width of 7.5 mm. midway along the length of the prosoma. In shape the metastoma is elliptic oval, with a truncated, concave anterior end and sharply rounded obtuse antero-lateral areas. Immediately in front of the metastoma occurs the mouth area, and

EURYPTERIDS FROM ENGLISH COAL MEASURES.

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a narrow depression runs towards the anterior border of the prosoma, from which arise the pro somal appendages. Surrounding the metastoma are the gnathobases of the ectognaths, or sixth paired appendages. Whilst that on the left has been pushed over the metastoma, that on the right shows a sharp junction with the lateral borders of the metastoma, and extends forward as far as the anterior border of the latter. In general outline the gnathobases appear sub-trigonal. The ectognath to the left of the specimen is complete, showing seven articulating joints, with a terminal palette which appears smooth in outline, oval, and probably ends in a blunt point. Specimen 30250 clearly shows the junction of the palette with the preceding joint. A corresponding limb to the right of the specimen is indistinctly seen lying close to the mesosoma, the pallette being partially visible. Of the remaining four pairs of pro somal appendages (or endognathites) the basal joints or coxae can be seen. To the left of the specimen the fifth paired appendage is represented by four well developed joints, the articulating junctions being visible. The contact with the fifth coxa is indistinct. The corresponding appendage to the right of the specimen shows the basal coxa within the head region, whilst joints seen to end in an elongated spine-like process, emerging from beneath matrix, may belong to this appendage. To the left of the specimen there are two joints in contact with the fourth basal coxa, but although the fourth coxa is present to the right, it is not seen in contact with any joints. The matrix to the right of the prosoma shows upon its surface some small joints, the last of which is elongated, lying close to the border of the prosoma. This latter joint is longitudinally striated, and lies in an anterior posterior direction, and it is suggested that this may be related to the fourth paired appendage. Evidence of the third appendage is provided by several joints united to the basal coxa. This appendage, however, is better seen to the right of the specimen, where the coxa is seen to end near the lateral border of the prosoma. A series of small rectangular joints, probably five in number, extend over the border of the prosoma, as though running from the third coxa; they turn sharply to end in a terminal process, which is elongate oval in shape. The coxa of the second appendage is doubtfully visible to the right of the median depression, and may extend antero-laterally to near the anterior margin of the prosoma. Behind the prosoma above described occurs the outline of the opercular plate, formed by the anchylozed first and second segments of the mesosoma, providing the accessory pieces and lateral alae respectively. The line of junction can be traced on the present specimen. The anterior border of the opercular plate is convex, whilst the posterior border is slightly concave, giving a maximum length centrally of approximately

370

I•• R. MOORE,

9 mm. The antero-Iateral margins are broadly rounded, the curve straightening slightly on the lateral margins, and meeting the posterior border with an included angle of slightly less than 90 degrees. The median process consists of an anterior triangular portion, the apex of which is in line with the junction of the two portions of the opercular plate, and situated I mm. from their anterior edge. With an included angle of 90 degrees, it has a maximum width of 4.5 mm., from which point it tapers posteriorly. The total length of the appendage preserved is 10 mm., but the general appearance suggests a greater length. On either side of the tapering posterior portion of the border of the appendage occurs a spatulate plate, with a triangular anterior border fitting into the angle formed by the junction of the anterior and posterior portions of the median appendage. The one lateral border of these plates conforms to the shape of the median continuation, whilst the other is gently rounded to give a maximum width of 2 mm. Postenorly, these plates disappear beneath the third mesosomal segment. Bordering the anterior part of the median appendage are indications of the presence of two triangular plates, with their base along the anterior border of the opercular plate. The whole of the prosoma, together with the operculum and median appendage, appears to be covered with very minute scales unlike the coarser ornamentation of the dorsal prosoma and mesosoma. Segments of mesosoma. The complete mesosoma is shown on the impression (No. 30250) and consists of six segments giving a rather rectangular appearance. Along the anterior edge of each segment is produced a very distinct ridge showing the amount of overlap of the segments. The first mesosomal segment is shorter than the rest, whilst its lateral margins tend to show a curve. The lateral terminations of the second and third segments are obscured by fragments of the opposite positive surface. The fourth segment is the longest, whilst the fifth is well developed with its lateral margins produced in a curve directed slightly outwards and backwards, so that the posterior edge of the fifth segment extends nearly 2 mm. beyond the anterior edge of the sixth segment. Similar characters are shown by the sixth segment, but its marginal spine is more strongly developed. This is clearly seen on both the impression and positive specimens. The mesosoma presents a slightly tumid appearance centrally, decreasing in a posterior direction, whilst the lateral portions of the segments are flattened. Poor indications of the median appendage are seen on the dorsal impression in the form of a slightly elevated triangular ridge extending into the third segment. The ornamentation is distinct, being minute on the anterior part of each segment, but rapidly developing posteriorly to the characteristic broadly triangular squamae, showing a

EURYPTERlDS FROM ENGLISH COAL MEASURES.

371

regular distribution. This is better seen on the positive surface of the specimen 30249. The lateral margins of the fifth, and sixth mesosomal segments show a development of oblique striae, which in the case of the last segment extend into the apex of the spine. Segments of meiasoma. The seventh segment or first metasomal is not so well preserved, but shows a width very little less than the preceding segment. It is characterized by powerful backward and outwardly directed spines, each being bounded by a definite line, and apparently not continuous with the segment. Indications suggest similar spines on preceding segments. This segment shows evidence of intumescence in the form of a slightly raised area, the base of which rests on the posterior border, and its sides slope gently forward from the spinal process. A similar feature was noted by Stainer (1915, p. 639) on his Eurypterus dumonti. The posterior part of the specimen is badly preserved, but portions of three further metasomal segments, which are much narrower than the first, are visible. The width of the second metasomal segment appears to have been about 13 mm., with a length of 6 mm. Ornamentation has been preserved in a few areas, where it it seen to be similar to that of the mesosoma. The occurrence of another undoubted species Eurypterus derbiensis H. Woodward 1907, at the same locality is noteworthy, but this is represented only by a very small specimen which possesses a sub-quadrate prosoma, somewhat arched segments, and a crenulate ornamentation of the metasomal segments. Of the British species E. moyseyi appears most closely related to E. wilsoni. Though the latter is a larger species, there is a similarity of form both of the prosoma and mesosoma. The eyes similarly placed in both species are larger and more prominent in E. moyseyi than in E. wilsoni, whilst the former species shows much stronger features in the region of its prosoma. Evidence of the median appendage is present as rounded raised prominences on the posterior portions of the second, third and possibly the fourth segments of E. wilsoni. E. moyseyi, however, shows triangular ridges on the anterior portions of the corresponding segments. The ornamentation of the two species is similar, though that of E. moyseyi is more strongly developed on the prosoma. In general proportions E. moyseyi is similar to E. mansjieldi C. E. Hall 1877, but like E. wilsoni differs in its ornamentation. Moreover, E. mansfieldi does not show the two small spatulate plates associated with its median appendage as does E. moyseyi. The presence of numerous small tubercles over the posterior portion of the carapace distinguishes E. pennsylvanicus J. Hall (1884) from both E. mansfieldi and E. moyseyi.

37 2

L. R. MOORE,

Meek and Worthen (r868, [1] p. 544) described and figured a peculiar Upper Carboniferous Eurypterid from Mazon Creek, Illinois,' which by the possession of two spatulate plates associated with the median appendage was accorded sub-generic rank Eurypterus (Anthraconectes) mazonensis Meek and Worthen. This species shows seven large segments with a very sharp decrease in width to the two succeeding segments. The terminology used throughout this paper is that adopted by Dr. Leif Stermer (1934), so that the American specimen may be considered as showing a complete mesosoma together with three metasomal segments, the first of which is considerably larger than the two succeeding segments. E. moyseyi shows many features in common with E. mazonensis, exhibiting a similar median appendage with spatulate plates. Though this appendage in E. mazonensis extends into the sixth mesosomal segment, whilst in E. moyseyi it is traced only definitely to the third, this difference may be due to sex as pointed out by H. Woodward (r872, p. 142). E. mazonensis is a somewhat larger species with segments which, in their shape and the strong development of spines on the seventh or first metasomal, with weaker indications on the preceding segments, show a great resemblance to those of E. moyseyi. The prosoma of E. mazonensis shows a prominent concavity of its anterior margin, with sinuation of its lateral borders, and swollen genal spines extending backwards to embrace the first and second mesosomal segments. These features are not known in E. moyseyi. However, the general character of the ventral surface of the prosoma is similar, the metastoma and gnathobases being of the same shape, whilst the ectognaths end in a broad palette. Meek and Worthen (r868, [1] p. 545) describe the third, fourth and fifth paired endognaths of E. mazonensis as ending in a single-pointed dactylus. It is possible that the fourth and fifth paired appendages of E. moyseyi terminate in an ovalshaped joint.

GENERAL CONSIDERATIONS. The available material of Upper Carboniferous Eurypterids is very scanty, whilst knowledge of these forms is correspondingly incomplete. Hence it becomes particularly difficult where specimens are rare to estimate the importance of individual variation. How far any variation may be ascribed to sex adds further complication. However, it would appear that E. mazonensis, E. mansjieldi, E. wilsoni and E. moyseyi provide % I am indebted to Stephen H. Jones, Esq., M.Sc., who informs me as to the horizon of these beds; "The Mawn Creek beds of Illinois = Alleghany Series, which corresponds to the uppermost Westphalian of Europe (Westphalian D), i.e., including part of the Radstockian of England." E. mansfieldi and E. stylus J. Hall, 1884, occur at a comparable horizon. The order of these species was incorrectly given by Stainer (1915, p, 642) in the second division of his grouping of Carboniferous E urypterids.

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a very closely related gro up of species, all of which show some simila rity in sha pe and general proportions. Th eir orn amentat ion is compa ra ble, th at of E . man sfi eldi being more st rongly developed than in all other species. The pre valence of spines, particularl y on the posterior segments, is a n in teresting feature common t o all the species. These spines a re themselves ornamented by oblique st riae. In E . moyseyi such a spine is pres ent on the first metasomal segment, apparently divided from the segment by a line, and givi ng the impression that the spine might readily be broken off. H ow far the ends of the segments have in man y cases thus suffered is uncerta in, though H all 's figures of E . mansfieldi suggest th e former presence of spines. E. mansfieldi a nd E . mazonensis have rathe r distinctively shaped pro soma s, whilst in this char acter E . wilsoni resembles E. moyseyi. Th e ventral surfaces of E . ma zonensis a nd E. moyseyi show st riking resemblances, particularly in the form of the opercular plate and median appendage with its pair of spatulate plates. These plates had hitherto only been found in E. mazonensis, and led to Meek and Worthen suggesting the sub-genus Anthraconectes. Both Woodward and Hall regarded this feature as merely of specific valu e. Howe ver , Clark and Ruedemann (1912, vol. I, p. 219 ) agreed with Meek a nd Worthen that a sepa ration from true E urypterus should be made, but regarded the preservation of the median organ to be such as to lea ve it s characters doubtful. The undoubted occurrence of these spa tu la te plates in E. moysey i is therefore a t once very interestin g and of some impor ta nce. These plates are not known in E . mansfieldi, which has a median appendage, the extremity of which is qu adrilobed (J. Hall, 1884, p. 32). There is therefore, a grea t degr ee of differenc e in this char acter between E . man sfieldi a nd E. mazonensis , though both species retain similar dorsal fea tures . The Bri tish species of this group apparently bear closer resembl ance to each other tha n do the American species, although t he ventra l surface of E. wilsoni is unknown. It is interesting t o note that Pruvost (1930 , pp. 194) described a new species of E urypterus from t he Coal Measures of Cha rleroi (Westphalian B), which he nam ed Eurypterus (A nth raconectes) Cambieri. This specimen shows many characters in common with E. moy seyi, He recognized at the same time a specimen of E. moys ey i, the comparison being made with Woodward's figures of that species. It is clear therefore that workers on the Continent are dealing with specim ens from the Coal Measures, which show marked affinities to the group of species discussed above. The known Upper Car boniferou s species, however , exhibit some di versity in their ex treme form s; particularl y is this the case in the character of the prosoma. E . man sfieldi shows a

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rounded anterior border to its prosoma, whilst E. dumonti Stainer (191S, p. 639) and E. derbiensis both show sharply quadrate forms. I The ornamentation varies from squamae in E. moyseyi and E. wilsoni to the tubercles of E. dumonti and E. granosus Jordan and Von Meyer (18S6, pp. I-IS, pls. T, II). It is interesting to note that two Lower Carboniferous forms. E. scabrosus H. Woodward (1887, p. 481, pI. XIII), and E. scooleri Hibbert 1836 (see Woodward, 1872, pp. 133-139. pIs. xxv-xxvii), show a stronger tuberculate ornamentation than any known Upper Carboniferous forms. The ornamentation and tendency to the production of spine-like processes on the segments of Carboniferous forms. did not escape the notice of Clarke and Ruedemann (1912, pp. 221-2), who regarded them as of phylogenetic significance; it is however, interesting to note that the Eurypterids of the Coal Measures are generally small. The change of habitat from marine to the brackish or freshwater conditions of the Coal Measures, meant the re-adaptation of a race which had passed its acme. It is perhaps to this adaptation that the addition of ornament and the occasional occurrence of extreme types must be ascribed. Moreover the features shown by all Coal Measure Eurypterids, together with their mode of life, justify the raising of these forms to sub-generic, if not generic rank. The sub-genus Anthraconectes suggested by Meek and Worthen for Eurypterus (Anthraconectes) mazonensis, and later adopted by Clarke and Ruedemann (1912, vol, I, p. 222) for all Carboniferous forms, is available. Stainer (191S, p. 642) suggested a tripartite grouping of Carboniferous Eurypterids, but his arrangement was largely stratigraphical. The species discussed here fall into the latter portion of his second group. REFERENCES. CLARKE, J. M. and R. RUEDEMANN. 1912. The Eurypterida of New York. Memoir 14. New York State Museum. Vols. i. and ii. HALL, C. E. 1877. Proc. Amer. Phil. Soc. Philad., vol. xvi., p. 621. (See also J. Hall, 1884.) HALL, J. 1884. Note on the Eurypteridee of the Devonian and Car-. boniferous Formations of Pennsylvania. znd Geol, Suru. Pennsylvania, Rep. Progress, 1884, pp. 23-39. HIBBERT, S. 1836. Trans. Roy. Soc., Edinb., vol. xiii., part i., p. 280. JORDAN, H. and H. VON MEYER. 1856. Ueber die Crustaceen der Steinkohlenformation von Saarbrucken. Palaontogra-ph ica, vol. iv., pp. I-IS. pIs. i-ii. MEEK, F. B. and A. H. WORTHEN. 1868. [1] Geol, Suru. Illinois, vol. iii., Geology and Palseontology, p. 544-547. - - - . 1868. [2] Am. Jour. Scie., vol. xlvi., p. 21. I This latter feature is shown greatly exaggerated in Glaucodes nuuhieui- Pruvost 1924, an unusual form found in the Coal Measures of Charleroi.

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~IEASURES.

3i5

l'RUVOST, P . 1924 . U n Eurypt eride n ou ve au du T errain houiller d e Ch arleroi. .Ann ales de la Societe Geologique du N ord, T. xl viii., p. 143· - - -- a n d RE NIER, A. 1930 . Memoirs du Mu see Royal D 'histoire naturelle de B elgique Memoire No. 44 , pp. 194, p I. x iii ., figs . I , ra• .HE USS, A . E. 1855. Ueber cine neu e K r us ters pecies a us der B ohmischen Stein k ohle nfor mat io n. D enkschr. K. -K. Akad., W issensch. Wien , vo l. x. , pp. 81-83, pI s . iii.-iv. STAINER, X . 1915. On a n ew E urypterid from the Be lgian Coal Measures . Quart . f ourn , Geol , Soc.. vol. lxx i., pp. 639-6 47 . STOR:\IER, L . 1934 . .. Merostomata from the Downtonian Sa n ds t one of R in geri ke, Norway." Skrifter utgitt av D et Norske Vi denskap sA kademie i Oslo, I Matem .-Natur vid, Klasse, 1933, No . 10. WOODWARD, H . 1872. A Mo nog ra ph of the Brit ish F ossil Crus tacea of the order Mer ostornata . Pal. Soc. - -- - . 1887. On a n ew species of Eurypterus from t he L ower Car bon ifero us shales of Glenc ar t h olm, E skdal e, Sco t la nd . Geol. Mag., pp. 481-484 . p I. x iii. 1888. Note on E uryp t erus from the Carbonifer ou s . Geol. Mag., pp. 419 -421 . - -- 1907. Two n ew species of Eurypterus from the Coal Mea sures of Ilkeston, D erbysh ir e . Geol, Mag., pp. 277 -2 82, pI. xiii, EXPLANATI ON OF FIGURES 58-64. F IG. 58. Eurypterus wilsoni W oo dward It approx . size . From Carnerton Collie ry, Upper Coa l Mea sures (Rads t oc k Series ) of So me rset. Specim en No. Ca. 7193 in the collection of the Bristol Muse um and Art Gall ery. FIG. 59. E urypterus cf. wilsoni Woodward N atural size. T h e actua l specim en from the N O. 3 seam Bromley Colliery. Upper Coa l Measures (F arring ton Series) of So me rset. Sp ecimen No. In. 356 10, in the collec t ion of the B ri t ish Museu m (Natural History). FI G. 60 . Eurypterus d . wilson i W oodward . N a t ural size . T he impressi on of the specimen sho wn in Fig. 59 . Specime n No. Cb , 2552, in the colle ct ion of the Bristol Museum a nd Art Ga llery. FIG. 6 1. E urypterus d . unlsoni W ood ward X 3 . Enlargement to sho w the orname ntat ion of the p osterior portion of the prosoma, fir st, secon d a n d third m esosomal seg me nts of spec ime n shown in Fig. 59 . FI G. 62. Eurypterus d . tuilsoni Woodward X 3. Enlargement sh owing the ornamentation of the metasomal segme nts of the specimen sh own in F ig. 59. FIG . 63. E urypterus moyseyi Woodwa rd x }. Showing the dorsal surface of a spe cimen fro m t he Shi p ley Cla y Pit, Llkeston, D erbyshire . Specim en No. 30250 in the collec tion of the Geological Survey. FIG. 64. Eurypterus moy sey i W oodward x ~ . Sh owing the ventral aspec t of the prosoma an d r egion of the opercular plate, of the specimen sh own in Fig. 63. Sp ec im en No. 3024 9 in t h e coll ection of the Geological Survey.

PROC. GEOI.. As soc.,

V OL.

XLVII., P ART 4, 1930.