ECHINODERMATA - KU ScholarWorks - University of Kansas

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26 THE UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS base. Basal circlet broadly conical in side view, pentagonal in basal view, 3 mm. long by 5.5 mm. wide, with three normally disposed basais. Radials five, pentagonal in side view, rounded V-shaped or lobate in top view, each 5.5 mm. long by 4 mm. wide, with short wide shallow sinus on summit 2 mm. long by 4 mm. wide, and longer limbs on anal side than on the other sides. Deltoids four, elongate, lancet-shaped, each 3 mm. long by 1.5 mm. wide, not visible in side view, with approximately nine hidden hydrospire slits on each side of an ambulacrum, extending aborally in the radial limbs. The deltoid crests are exposed between side plates, the lips being exposed around the oral opening, and the aboral ends of the hydrospire slits exposed on the margins of the radial sinuses, but otherwise most of the summit is covered by the broad lancet and side plates. On the anal side two deltoid plates appear to be present—a hexagonal epideltoid adjacent to the oral opening with two aborally disposed anal septa, and a pentagonal hypodeltoid plate on the aboral side of the anal opening that abuts against the truncated radial limbs and is covered over in part by the side plates. Hydrospire slits are absent on the anal side, thus there are eight hydrospire fields. The adorai ends of the spiracular slits are prominent and have the appearance of five spiracles. Ambulacra five, broad, petaloid, each 4.5 mm. long by 4.5 mm. wide, with lancet completely exposed, and side plates extended almost to the margins of the deltoids and radials, separated from them by a narrow spiracular slit. Each primary side plate is elongate quadrangular, with a small triangular secondary side plate on the abmedial-adoral corner, and 40 side plates in 10 mm. The surfaces of the calyx plates are ornamented with fine growth striae parallel to plate margins. FIGURES 12-17. Cryptoschisrna schultzit (D' ARcumc & DE VERNEUIL), Devonian, Spain (depositories listed at end. 12. Anal view, slits not shown, X15 (no. 311). 13. Oral view showing plates around anal opening and structures of the "DE" interambulacrum and "E" ambulacrum, X15 (no. S3,224). 14. Proximal part of calyx and column seen from "AB" side, showing azygous basal and subbasal plates, X9 (no. 311). 15. Vertical thin section of an ambulacrum showing lancet and side plates with hydrospire and radial limb on one side, X15 (no. E1,063b). 16. Lancet and side plates of part of "E" ambulacrum, X45 (no. 311). 17. Lancet and side plates of part of an ambulacrum, X37.5 (no. S3,224). [Explanation.—An, anal opening; Bf, brachiolar facet; Bp, brachiolar pit; Db, deltoid body; Dl, deltoid lip; Ds, deltoid septum; ED, epideltoid; HD, hypodeltoid; L, lancet; 0, oral opening; OSp, outer side plate; R, radial; SB, subbasal; SFg, side food groove; Sp, main side plate; Ss, spiracular slit; Z, azygous basal.] Depositories: Harvard Mus. Comp. Zool., no. 311; U. S. Natl. Mus., no. S3,224; British Mus. (Nat. History), no. E1,063b. 1 7 15
BLASTOID STUDIES 27 The description is taken mainly from one specimen illustrated on Plate 3, figures 7-9. Remarks.—The genus Cryptoschisma was probably derived from Pentremitidea by outward migration of the lancet plate to the surface of the calyx and fusion of the subdeltoid and superdeltoid into an epideltoid. Occurrence.—Devonian, Spain; Calizas de Arnao, Saber°, and Calizas des Ferrofies, Le6n and Asturias. Types.—Topotypes, 311, six specimens, DeKoninck collection, old no. 2,357, Sabero, Spain, Harvard Museum of Comparative Zoology, Cambridge, Mass.; 220, three specimens, old no. 857, J. M. Barnard collection, labelled Eifel, in Harvard Museum; and S3,224, 20 specimens, Springer collection, Asturias, Spain, and S3,225, 16 specimens Springer collection, León, Spain, in U.S. National Museum, Washington; E1,063b, thin section, British Museum Natural History. Genus DECASCHISMA Fay, n. gen. Type-species, by original designation (herein).—Codaster pentalobus HALL, 1882 (adv. pub!., 1879). Generic diagnosis.—Fissiculate blastoids with ten exposed hydrospire fields, superdeltoid, subdeltoid, hypodeltoid, lancet covered by side plates, exposed spiracular slits, calyx conical in side view. Silurian, Indiana. DECASCHISMA PENTALOBUS (Hall) Plate I, figures 7-10; text-figs. 18-20 Codaster pentalobris HALL, 1879, p. 13; 1882, p. 69. Description.—Calyx calcitic, obconical in side view, pentagonal in top view, 17 mm. long by 13 mm. wide, with vault 5 mm. long, pelvis 12 mm. long, and pelvic angle 50 degrees. Periphery well above mid-height at radial lips. Stem impression worn, but in one specimen it appears to be round, smooth, about 1 mm. in diameter, with a small round central lumen. Basal circlet elongate conical in side view, rounded pentagonal in basal view, 6.5 mm. long by 7.5 mm. wide, with three normally disposed basals and small flat truncated aboral end. Radials five, elongate hexagonal, each strongly lobed, giving the calyx a broadly stellate appearance in top view, with short limbs on anal side. Each radial is 11 mm. long by 5.5 mm. wide, with broad, deep, short sinus 5 mm. long by 3 mm. wide by 2 mm. high, projecting ventrally into low corona l processes except on the anal side. Radials overlap deltoids. Deltoids four, short, lancet-shaped, not visible in side view, each 2 mm. long by 2.5 mm. wide, with wide V- shaped deltoid lip, low medium septum, high deltoid body, and seven or eight hydrospire slits on each side of an ambulacrum with four or five exposed, the slits extending across the adjacent radial limbs. On the anal side there are three deltoid plates, a superdeltoid, subdeltoid, and hypodeltoid. The superdeltoid is adjacent to the oral opening, is broadly arrow-shaped, and adjacent to lancet plates on each side. It is overlapped internally by a thin long V-shaped subdeltoid, which is extended on either side of the wide anal opening, beneath marginal parts of the adjacent lancet plates. The subdeltoid limbs are overlapped by the truncated radial limbs aborally, and on the outside, the long wide pentagonal hypodeltoid plate covers the subdeltoid limbs. The hypodeltoid can be seen in side view, is low, abuts against the radial limbs, and is approximately 4 mm. long by 4 mm. wide. Internally, the subdeltoid limbs and adjacent radial limbs are infolded into approximately three hydrospire slits on either side of the anal opening. Thus there are three anal deltoids and ten hydrospire fields, with a reduced number of slits in the two fields on the anal side. Ambulacra five, short, linear, each 7 mm. long by 1 mm. wide, with lancet covered by side plates and 36 side plates in 10 mm. Side plates normally disposed, with a subtriangular secondary side plate on the abmedial-adoral corner of each subquadrangular primary side plate. The surfaces of the calyx plates are ornamented with fine growth striae parallel to the margins. Remarks.—The genus Decaschisma appears to have been derived from Polydeltoideus by fusion of the two cryptodeltoids into a single subdeltoid plate. Occurrence.—Silurian, Waldron Shale, Waldron, Indiana. Types.—Topotypes, 2,554, eight specimens, Washburn collection, Walker Museum, University of Chicago, Chicago, Ill. The description is based upon characters seen in the specimen figured on plate 1, supplemented by features of the other specimens. DECASCHISMA PULCHELLUM (Miller & Dyer) Plate 1, figures 1-3; text-figs. 21, 22 Codaster pulchedus MILLER & DYER, 1878, p. 35, pl. 2, figs. 13, 13a. Description.—Calyx calcitic, obconical in side view with flaring base, pentagonal in top view, 10 mm. long by 7.5 mm. wide, with periphery well above mid-height at radial lips, vault 2 mm., pelvis 8 mm., and pelvic angle on basals 95 degrees, but on radial bodies 25 to 30 degrees. Stem impression small, round, crenellar, 0.5 mm. in diameter, on small flat triangular aboral portion of basals. Basal circlet widely flaring, almost cup-shaped in side view, 3.5 mm. long by 6 mm. wide, strongly triangular in basal view, with a sharp ridge in the middle portion of each basal plate extending to aboral end, forming a sharp triangular base about 1 mm. in diameter. The geometric center of each basal is flared outward, giving a bluntly conical shape to the base in side view. Radials Five, elongate hexagonal to subquadrangular, each 7 mm. long by 4 mm. wide, with short, deep, wide sinus 2.5
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