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A New Genus of Characeae and New Merostomata from the Coal Measures of Nova Scotia

A New Genus of Characeae and New Merostomata from the Coal Measures of Nova Scotia[1]

By W. A. Bell, Ph.D.

Presented by E. M. Kindle, A.B., M.Sc, Ph.D., F.R.S.C.

(Read May Meeting, 1922)


Introduction

The plants and animais that lived in Coal Measures time make a special appeal to our imagination. For the first time in geological history we have records that enable us to picture large areas of land not as barren rock masses whose nakedness we fain would cover had we but the knowledge, but as living landscapes in which broad meandering rivers gleam amidst forests that are strange indeed to modern eyes, but that rival ours in majesty of form and size, and in potential importance to mankind.

Industrial exploitation of the long buried debris of these ancient forests for their use as fuel, has been the chief aid in satisfying our curiosity about the relationships and habits of numerous individual members of the Coal Measures plant and animal societies. Finally our knowledge has become sufficiently complete to enable us to recognize a succession in time of terrestrial dynasties during the Coal Measures and to apply this wisdom to the furtherance of new exploitation for coal.

The present paper is a brief description of several forms of this ancient life from the Coal Measures of Nova Scotia, whose remains are rare. The first to be considered are minute fruit bodies of algæ-like plants that were found by Dr. A. O. Hayes in the shale roof of a five-foot seam of coal at the St. Rose mine, Inverness county. They record the earliest known occurrence of the Charophyta or stone worts—a phylum that embraces the recent Chara, common in freshwater ponds, lakes, pools, and brackish water lagoons of to-day. In the same beds Dr. Hayes was fortunate enough to discover a carapace of a Schizopod crustacean, somewhat better preserved than the specimen that was collected by Sir J. W. Dawson from the Joggins. These two species come from the lower part of the Coal Measures.

The two remaining species described come from eastern Cape Breton from a higher horizon. One is the carapace of a species of Eurypterid whose near allies have been found at an equivalent horizon in Pennsylvania, and in England. The présence of Eurypterids, a rapidly declining race, in Nova Scotia, had already been indicated by the previous discovery of several fragmentary abdominal remains. The other form under consideration is an odd one of doubtful relationships, but which invites comparison with such shield bearing Merostomata as the Xiphosurids or sword-tails.


Phylum Charophyta

Genus Palaeochara

Palaeochara n. g.—Oogonium like Chara, but with six, instead of five spirally wound investing cells. Genotype Palaeochara acadica.


Palaeochara acadica n. sp.

Description: Oogonium subglobular to pear-shaped with hemispherical base and conical apex. Length somewhat exceeding the greatest diameter. Investing cells six in number, commencing around a smooth, circular, basal area and making one cpmplete spiral turn to the raised conical end. Six or seven spiral ridges visible on a side view. Length 0.55 mm.; diameter 0.53 mm.; diameter of smooth basal area 0.075 mm.

Locality: St. Rose mine, Inverness county, N.S.

Horizon: Coal Measures.

Remarks: The remains of the oogonium are now preserved as iron pyrites, inferred to be a pseudomorph after calcite. Thin sections examined under reflected light clearly show the Chara affinities of the fossil in that the oogonial investment consists of partial infillings of former spirally wound elongate cells. The position of the former walls of these cells is revealed in section either as oblique or transverse lines of parting, and in surface view by narrow grooves on the spiral ridges. The latter appearance of the surface indicates that the original calcareous deposit grew from initial deposition against the concave inner borders of the cells as in recent Chara. In recent Charas the lateral walls break down as the fruit matures, so that a continuous shell of lime finally surrounds the oospore. In Palaeochara the lateral walls evidently persisted to a greater extent. The interior of the oogonium is now filled with infiltrated calcite. The basal circular area from which the spirals spring is a sunken pit, or foramen, and probably indicates the former position of attachment of the stalk cell.

There is seemingly also a minute open pore and narrow slits between the cells at the apical end since a specimen treated with dilute hydrochloric acid admits the acid to the interior with the consequent solution of the infiltrated calcite and ebullitions of gas through the neck. The neck, however, is wholly or partly broken off in the majority of specimens. Lengths vary from 0.5 to 0.6 mm., diameters from 0.45 to 0.55 mm.

The presence of an undoubted representative of the Characeae in the Carboniferous is of great interest in connection with the occurrence of minute spirally marked globular organisms, about 1 mm. in diameter, in association with marine fossils in Middle Devonian limestone of Ohio. These were first reported by Meek[2] in 1873 from the falls of the Ohio who assigned them with some doubt to the freshwater genus Chara and was of the opinion that they drifted out to sea. Williamson[3] in 1880 examined similar forms from Kelly's island, Ohio, under the impression that they might be of vegetable origin, but came to the decision that they were foraminiferal and included them in his genus Calcisphaera which had been created to hold somewhat similar globular forms from the Carboniferous of Wales. He named the Ohio forms Calcisphaera robusta. Dawson[4] a few years later, in 1883, pointed out important characters in which the American species from Kelly's island differed from Williamson's description of them. Although Dawson remarks on the superficial resemblance to Chara fruits he agrees with Williamson in referring them to the foraminiferae, but he assigns them to the genus Saccamina as Saccamina eriana. Knowlton[5] in 1889 redescribed the species from the Falls of Ohio and presented at length the various conflicting views held regarding its affinities. The major difficulties against the Characeous affinity are stated to be the presence of nine or ten spiral markings instead of the five in recent and known fossil Chara, the twist of the spirals in a right handed instead of a left handed direction, and finally the abundant uniform distribution of the fossil in a marine formation. In conclusion Knowlton distinguishes the Falls of Ohio form with the name Calcisphaera lemoni. In his review Knowlton failed to recognize the description of the Falls of Ohio species presented by Ulrich[6] three years earlier in 1886. The latter makes no mention of the Chara-like appearance of the organism and includes them in the foraminifera under a new genus Moellerina as Moellerina greenei. The number of spirals are stated to be eight or nine. Ulrich's description and figures surpass in detail and accuracy any so far presented, and after a study of the Kelly's Island species the writer is convinced that Ulrich's description is applicable also to it. One discrepancy, however, is noted. Whereas all the specimens from Kelly's island examined by the writer, and apparently those by Knowlton from the Falls of Ohio, have a right handed spiral twist to the ridges, Ulrich figures one with a left handed twist. Only nine spirals were observed by the writer in the Devonian specimens to which he had access. But the number of spirals, as evident from the discovery of Palaeochara, does not mitigate against a possible Characeous affinity of this fossil. A much more serious objection may be raised. A feature carefully noted by Ulrich, and confirmed by the writer for the Kelly's Island species, is the presence not of a thick single wall as interpreted by Williamson, Dawson, and Knowlton, but of two thin walls with a broad intervening space, the inner spherical cavity communicating with the exterior by tubular prolongations of the inner wall at each end. The spiral ridges are restricted to the outer wall, and are a part or ornamentation of the wall itself, so that they afford no evidence of a Chara construction in support of the superficial appearance.


Class Crustacea

Subclass Eucrustacea

Anthrapalaemon hillianus Dawson

1877—Anthrapalaemon (Paloeocarabus) Hilliana, Dawson, Geol. Mag. Dec. 2, Vol. 4, p. 56. Figure 1.

1878—Anthrapalaemon (Paloeocarabus) Hillanus, Dawson, Suppl. 2nd ed. Acad. Geol. p. 55. Figure 10.

Description: (Based on a flattened carapace.) Carapace barrel-shaped, subquadrangular, greatest width exceeding the length exclusive of rostrum. Anterior margin straight, furnished with three marked spines, one rostral, long and thin, triangularly keeled, and an antero-lateral spine on each side, short and stout, flattened, diverging outwards from an angle of 30°. Lateral margins conversely rounded, provided in the anterior one-third with short spines or serrations, directed forwardly. Posterior margin, grooved, concavely rounded, joining the lateral margins in bluntly acute angles.

Original curvature of carapace destroyed by pressure but a raised gastric region still indicated. The lateral margins are bordered by a depressed band which broadens towards the antero-lateral corners. Anteriorly a distinct V-shaped cervical furrow joins the two flat marginal bands and divides the carapace into two unequally sized areas. The anterior of these areas has three distinct spine-bearing ridges, a median one forming the base of the rostrum, which runs for half the distance to the cervical fold, and a pair of lateral ridges on either side, which are directed so as to converge when produced at a point near the forward end of the rostrum. These ridges abut on the cervical furrow but do not quite reach the anterior margin. The area behind the cervical furrow is marked by a very faint median keel which dies out entirely half a millimetre from the posterior border.

The surface viewed through a lens is roughly pitted, and the bases of larger spines lie on the rostrum and keels.

Dimensions: Extreme length 20 mm.; length, excluding rostrum, along median line, 13 mm.; length of rostrum projecting beyond anterior margin 5 mm.; width of rostrum at anterior margin 0.8 mm.; greatest width of carapace 17 mm.; apex of cervical furrow 7 mm. from the anterior border.

Locality: St. Rose mine, Inverness county, N.S. From roof of coal seam, associated with Naiadites, Ostracoda, and Palaeochara acadica.

Horizon: Coal Measures. (Lower Coal Measures?)

Remarks: Although the type spécimen of A. hillianus is proportionally narrower than the present one, the points of agreement are too many for varietal separation. Peach[7] has pointed out that in A. russellianus the serrations on the lateral margins are most probably the flattened spines that were borne along the whole length of lateral keels. As a result of the doublure of the test, and flattening accompanying fossilization, the serrations may appear to be restricted to the anterior portion of the carapace. This observation promotes caution in laying stress on the number of dentations visible on the margin, stated to be five on the type specimen of A. hillianus. The two strong spines figured by Dawson on either side of the base of the rostrum are seen in the present specimen to consist of two short spinous keels as present also in a similar position in A. russellianus and other species.

Dawson pointed out the close resemblance of A. hillianus to A. dubius (Prestwich). Yet the affinity must lie nearer A. grossarti Salter

when one considers the shape of the carapace, its ornamentation, the size of its marginal spines, and the faint representation of the median keel behind the cervical furrow. Woodward's figures of A. grossarti, unlike Salter's, show the cervical furrow quite distinctly, and a median keel precisely like that of A. hillianus. I retain the Nova Scotian species since it has a stronger curvature fore and aft of the lateral margins of the carapace. Thus, in the Inverness specimen, the antero-lateral angle formed by the anterior and lateral margins (neglecting the acute spine) is roughly 120° as compared with 110° in A. grossarti, too great a difference to be due to pressure. A. dubius, on the contrary, is readily distinguished by the absence of marked antero-lateral spines, the arcuate frontal margin, and the even, pronounced, strength of the median keel which runs to the posterior margin.


Class Arachnida

Subclass Merostomata

Eurypterus (Anthraconectes) brasdorensis n. sp.

Description: (Based on a single carapace.) Carapace, semiovate, with length nearly three-fourths the maximum breadth. The posterior margin very slightly convex backwards. Genal angles produced into short bluntly acute spines. Between the prominent reniform compound eyes there is a pair of elongate elevations which border a median depression in which lies a circular ocellar mound 1.3 mm. in diameter. This mound is situated directly in front of a line tangential to the posterior borders of the eyes and was apparently the seat of the ocelli. A second pair of elevations run obliquely from the middle of the posterior border towards the lateral margins, so that the eyes are situated in triangular, depressed areas of the test.

The surface is marked by raised scales or mucros on a finer shagreen ground. The individual outline of these scales is hemioval to hemispherical with their flat slopes facing anteriorly. In the posterior half of the shield, except in the depressed areas, the mucros are large, raised, more acutely pointed, and plainly visible to the unaided eye. Anteriorly and in the depressions, they are fine or microscopic, with much less relief. Adjacent to the lateral margins they become greatly elongated and flattened, and either border the margins in a parallel position or meet them obliquely at very acute angles. Anteriorly, the carapace is clearly folded underneath in a doublure and a faint, narrow, V-shaped ridge, situated medially close to the anterior margin, is probably due to the pressure from the ventral border of this fold. (Compare A. kidstoni.)

Dimensions: Greatest length 15.3 mm.; greatest width across genal angles 21.2 mm.; width across median ocellar mound 18.7 mm.; distance of median node from the posterior margin 6.4 mm.; distance of compound eyes from the posterior margin 7.5 mm.; long axis of compound eyes 3.1 mm.; short axis of compound eyes 1.5 mm.

Locality: Roof of four-foot seam, from dump derived from old slope, New Campbellton, Cape Breton.

Horizon: Upper Coal Measures or Radstockian (Upper Westphalian).

Remarks: Eurypterids are rare fossils from the Coal Measures the world over, and only some dozen species have been recorded.

The present species and an allied English Radstockian species Glyptoscorpius kidstoni Peach have carapaces agreeing in size, relative proportions, and ornamentation to that of Anthraconectes mansfieldi C. E. Hall from the Alleghany series. The resemblance is particularly close to those variants of smaller size figured by Jas. Hall as A. stylus. Specific identity, however, is withheld since nothing is known about the body of the Nova Scotian form. Accordingly, emphasis is placed on slight differences in outline of the carapace, distinctions that probably are inconstant and of doubtful specific value. The shield of our specimen has been so flattened by pressure that the anterior margin is covered, and accordingly it was not determined whether a short anterior spine similar to that borne by A. mansfieldi was present. The ornamentation of A. brasdorensis is identical in plan to that of A. kidstoni. In fact, the latter carapace differs only in its slightly greater proportional length and in the presence of a shallow indentation on the posterior border.

A carapace of an Eurypterid has not hitherto been described from the Coal Measures of Nova Scotia. Salter,[8] however, in 1863, assigned some fragments of Merostomatan abdomens to this genus, viz., E. ? pulicaris from the Little River group of St. John, N.B., a fragment of a large body segment comparable to E. scouleri Hibbert, from Port Hood, and an incomplete telson from Joggins whose resemblance to that of Hastimima whitei White from the Coal Measures of Brazil has been pointed out by Clarke and Ruedemann. The excellent preservation of the present carapace leads to the hope that the same horizon may yield further, and more complete, specimens of these ancient arachnids, whose race was rapidly approaching extinction.

The tendency of the Carboniferous Eurypterids to form dermal scale-like excrescences is given phylogerontic significance by Clarke and Ruedemann. Also these authors regard the subgenus Anthraconectes to be fresh or brackish-water inhabitants. A. brasdorensis

is associated at New Campbellton with abundant Anthracomya in a series of strata which present strong evidence of freshwater deposition.


SUBCLASS MEROSTOMATA

Genus Schistaspis

Schistaspis (σχιστός cloven; ἀσπίς shield)—Cephalic shield relatively large, hemispherical, smooth, with no distinct prominences or glabellar region. Paired median simple eyes doubtfully present near the anterior margin. Head shield articulated behind with a post-cephalic shield whose wing-like expansions are directed outwards and backwards. Abdominal free segments 8 (?) in number, non-trilobate, with spine-like posteriorly directed epimeral projections. The first seven abdominal segments are single. The last abdominal segment is anchylosed to a small hemispherical tail plate which doubtfully bore a telson spine in articulation with it.


Schistaspis bretonenis n. sp.

Description: Length, exclusive of possible telson spine, 27 mm.; maximum width 12.6 mm. Cephalic shield large, with hemispherical outer border, and concave, evenly curved posterior border. Genal angles acute but scarcely prolonged into a spine. Lateral margin with a narrow raised border which disappears, or is folded beneath, at the extreme front. Although the shield is crushed and somewhat fractured, there is no evidence of a raised glabellar region, nor could the definite presence of compound eyes be detected on the dorsal surface. Medially, however, and situated 1.1 mm. from the front margin there is a minute circular mound about 1/5 mm. in diameter which doubtfully may represent one of a pair of simple eyes. It lies a little to the left of the median line and the corresponding position to the right is obscured by a bit of matrix.

Behind the cephalic buckler and free from it, there is a crescentic shield whose anterior convex margin follows the contour of the shield in front. The lateral angles are acute but blunter than the cephalic genal angles. They lie about opposite the fourth abdominal segment. The posterior margin of this thoracic shield is triangular, the two straight edges enclosing in one specimen an angle of 116°, in the other an angle of 103°.

The first two visible abdominal segments are partly covered by overlap of the crescentic shield. The succeeding five segments are simple and free, with straight axial border in the frontal region of the abdomen but becoming arched in the posterior region. The

epimeral portions of these segments are defined from the axial portions in some segments by narrow, curved longitudinal grooves. They end in acute projections. The succeeding and last segment is formed of a fusion of somites. Anteriorly on this last segment there are two free epimeral projections. A small hemispherical tail-like area is marked by a median triangular depression suggesting articulation with a caudal spine which has been lost. In one specimen the entire posterior segment is lacking.

The total length of the abdominal portion is 8 mm., the width across the 4th segment 7.5 mm. On account of the partial covering of matrix and overlapping of the posterior shield there is a false appearance of a marked contraction of the body at the first two segments.

In the more complete specimen the cephalic shield has suffered rotation to the left and on that side overlaps all but the outer corner of the hinder shield. On account of this distortion and the presence of minute slips within the test it is difficult to trace the precise limits of the two shields in the axial region. Fig. 14 is a drawing to show more clearly the relations. A portion of the headshield a1 has been broken off and slipped under A. There is little evidence such as transverse wrinkling to indicate any important foreshortening, so that in its natural position shield A probably overlapped somewhat onto the anterior portion of shield B. A similar overlapping is apparent in the second specimen, although the margin of the fore shield is not complete. It seems evident at least that the two shields are not fused together in the axial region.

The shell substance is thin and lacks the scale-like ornamentation of the Eurypterids.

Although the general contour of the body and of the large cephalic shield resembles other Xiphosurians there is no apparent trilobation of the body and the presence of a distinct post-cephalic shield is unique. Were it not for the presence of the double shield and the absence of trilobation Schistaspis would be very similar to Belinurus, which has an abdomen of eight segments, of which the 7th and 8th are consolidated, in addition to a long, slender telson. Euproöps has seven abdominal segments fused together, besides a short caudal spine.

Explanation of Plate

Figs. 1, 2. Chara. Two specimens of a species occurring in a hot spring at Banff, Alberta. x 26.

Fig. 3. Palaeochara acadica n. sp. Side view x 26.

Figs. 4, 5, 6. Palaeochara acadica n. sp. View of basal ends of three specimens x 26.

Figs. 7, 8, 9. Palaeochara acadica n. sp. Longitudinal sections of three specimens viewed by reflected light. Note position of cellular walls, indicated by transverse or oblique lines of parting. Fig. 9 shows possible remnants of a diaphragm separating the neck cavity from the oospore. x 26.

Fig. 10. Anthrapalaemon hillianus Dawson. Dorsal view of carapace. x 2.

Fig. 11. Eurypterus (Anthraconectes) brasdorensis n. sp. Dorsal view of carapace. x 2.

Fig. 12. Schistaspis bretonensis n. sp. Dorsal view of holotype. x 2.

Fig. 13. Schistaspis bretonensis n. sp. Dorsal view of second specimen. x2.

Fig. 14. Schistaspis bretonensis n. sp. Drawing of holotype to indicate the fractures and slips within the cephalic shield. The corner a1 has slipped under the main body of the shield A.

PLATE I

TransRoySocCanada 16 4 plate 1.jpg

  1. Published by permission of the Director, Geological Survey, Ottawa.
  2. Meek, F. B., Geol. Surv., Ohio, Palæontology, Vol. I, 1873, p. 219.
  3. Williamson, W. C, Phil. Trans. Roy. Soc. Lond., Vol. 171, pt. 2, pp. 520-525.
  4. Dawson, J. W., Can. Nat., 2nd ser., Vol. X, 1883, pp. 5-8. Figure 3.
  5. Knowlton, F. H. Amer. Jour. Sci. and Arts, Vol. 37, 1889, pp. 202-209, Figures 1-3.
  6. Ulrich, E. O., Contributions to American Palæontology, Vol. I, No. 1, Cincinnati, Ohio, 1886.
  7. Peach, B. N., Monograph on the Higher Crustacea, Mem. Geol. Surv. G.B. Pal. Vol. I, No. 1, pp. 31-32, pl. iv. Figures 4, 6, 1908.
  8. Salter, Quart. Jour. Geol. Soc., Lond., vol. 19, pp. 78-79, 1863.

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