UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS PLATE 8 <strong>ECHINODERMATA</strong>, ARTICLE 3 FAY- BLASTOID STUDIES
BLASTO1D STUDIES 41 about one-third down from the top. The stem impression is obscure but appears to be round, 0.5 mm. in diameter, in a small depression. Basal circlet long, conical, 4 mm. long by 5 mm. wide, with three normally disposed basais. Radials five, elongate hexagonal, each 7 mm. long by 4.5 mm. wide, with deep, wide sinus 4 mm. long by 4 mm. wide; radials overlapping deltoids. Deltoids four, arrow-shaped, each 3 mm. long by 2.5 mm. wide, with seven or eight hydrospire slits on each side <strong>of</strong> an ambulacrum (except on anal side) extending to adjacent deltoid limbs parallel to the lancet margins and at right angles to the radiodeltoid sutures. The lancet and side plates cover a large portion <strong>of</strong> the hydrospire slits. The adorai tips <strong>of</strong> each deltoid are excavated by a narrow V-shaped notch, each side <strong>of</strong> the V leading to an open spiracular slit or hydrospire canal, similar to a paired spiracle. On the anal side there is an epideltoid and presumably a hypodeltoid (missing, but facets present). The epideltoid and other four deltoid lips surround the oral opening. The epideltoid is divided internally into two septa that separate the anal opening from the adjacent spiracular slits and four hidden hydrospire slits are present on each septum, extending to the adjacent radial limbs. Thus, ten hydrospire fields occur. The aboral part <strong>of</strong> the anal opening was presumably covered by a hypodeltoid plate that covered the epideltoid septa and abutted against the adjacent radial limbs. Ambulacra five, broad, petaloid, each 7 mm. long by 3 mm. wide, with lancet plate exposed almost its entire width, and 20 side plates in 10 mm. Each primary side plate is broadly quadrangular, with a rounded triangular secondary side plate on the abmedial-adoral margin <strong>of</strong> each primary side plate. An elongate side food groove extends from the admedial tip <strong>of</strong> each secondary side plate onto the lancet plate. There are six main coverplate sockets to each side plate along the main food groove on the lancet plate. The surfaces <strong>of</strong> the calyx plates are ornamented with fine growth striae parallel to plate margins. Occurrence.—Lower Carboniferous, Tournaisian, Tournai, Belgium. Types.—Plesiotypes, 19,082, three specimens, one <strong>of</strong> which (figured) was used for description, Gurley collection, Walker Museum, <strong>University</strong> <strong>of</strong> Chicago, Chicago, Ill.; S3,268, 11 specimens, Springer collection, U. S. National Museum, Washington. Genus PLEUROSCHISMA Reimann, 1945 Type-species, by original designation.—Pentrernites lycorias HALL, 1862. Generic diagnosis.—Fissiculate blastoids with ten exposed hydrospire fields, a superdeltoid, two cryptodeltoids, and a hypodeltoid, lancet completely covered by side plates, ambulacra extended downward along calyx, which is club-shaped in side view. Devonian, New York, Ontario. Rem arks.—The genus Pleuroschisma was probably derived from Polydeltoideus by downward growth <strong>of</strong> the lancet plates (toward base), thus forming a club-shaped blastoid from a conical form, and fusion <strong>of</strong> paradeltoids into part <strong>of</strong> the hypodeltoid. PLEUROSCHISMA ONTARIO Reiman,' Plate 17, figures 4-6; text-figs. 49, 50 Pleuroschisma ontario REIMANN, 1945, p. 25, pl. 6, figs. 2-3. Description.—Calyx calcitic, basal circlet missing, obconical in side view, circular in top view, 5.5 mm. wide, vault 4.5 mm. long, pelvis estimated at 5.5 mm. long, with periphery at radial lips. Radials five, elongate hexagonal, each 7 mm. long by 2.5 mm. wide, with wide, short, deep sinus 4 mm. long by 2.5 mm. wide by 1.25 mm. deep. Radial lip with thick raised ridge. Radials overlap deltoids. Deltoids four, lancet-shaped, each 2 mm. long by 1.5 mm. wide, forming a thin, low coronal process, with seven or eight hydrospire slits on each side <strong>of</strong> an ambulacrum, extending aborally to adjacent radial limbs. On the anal side four deltoids appear to occur. The hypodeltoid is missing because the specimen is slightly damaged in that region. The two high, thick, elongate, cryptodeltoids on either side <strong>of</strong> the anal opening rest upon the superdeltoid adorally and are overlapped by the radial EXPLANATION OF PLATE 8 FIGURE PAGE 1-6, 10, 11. Hyperob1astus filosus ( WHITEAVES), Devonian, Ontario; 1-6, 11, holotype, 3,660, Currie coll., identified by WHITEAVES, Geol. Survey Canada; Hamilton beds, near Thedford, Ontario; 1-3, oral, "D" ambulacral, aboral views, (all X5.1 ); 11, view showing the hypodeltoid in place ( X15.3).-4-6, hypotype, E16,209, Buffalo Soc. Nat. Sci.; Hungry Hollow Formation (coral zone <strong>of</strong> Wid- (1er beds), Thedford, Ontario; oral, "D" ambulacral, aboral views (all X6.7).-10, hypotype, E16,206, Charles Southworth coll., Buffalo Soc. Nat. Sci.; Hungry Hollow Formation (coral zone <strong>of</strong> Widder beds), Thedford, Ontario; aboral view <strong>of</strong> thin section showing hydrospires (X3.7) 32 7-9. Hyperohlastus filosus angustus (IthimANN), holotype, E15,403, Buffalo Soc. Nat. Sci.; Hungry Hollow Formation (coral zone <strong>of</strong> Widder beds), Thedford, Ontario; oral, "D" ambulacral, aboral views (all X5.9) 33