Smithsonian miscellaneous collections . Peristome.—Central to slightly posterior, pentagonal, pointed an-teriorly, truncated posteriorly. Adoral plate arrangement.—Plate sutures of basicoronal plates notvisible on all plates; basicoronal interambulacral plates separatedfrom postbasicoronal plates by two pairs of ambulacral plates (textfig. 24) ; 7 to 8 ambulacral, 3 to 5 interambulacral postbasicoronalplates in each series on adoral surface. Comparison with other species.—C. crassus is very similar to theliving species Clypeaster prostratus and is probably an ancestor of is sim
Smithsonian miscellaneous collections . Peristome.—Central to slightly posterior, pentagonal, pointed an-teriorly, truncated posteriorly. Adoral plate arrangement.—Plate sutures of basicoronal plates notvisible on all plates; basicoronal interambulacral plates separatedfrom postbasicoronal plates by two pairs of ambulacral plates (textfig. 24) ; 7 to 8 ambulacral, 3 to 5 interambulacral postbasicoronalplates in each series on adoral surface. Comparison with other species.—C. crassus is very similar to theliving species Clypeaster prostratus and is probably an ancestor of is similar in shape, size, petal arrangement, plate arrangement, andposition of apical system, periproct, and peristome. It differs mainlyin having a thicker margin. In C. crassus the margin is 10 percentof the length, whereas in the average specimen of C. prostratus itis percent of the length. In C. crassus the interambulacra aremuch more strongly indented at the margin in areas 4, 5, 1, and theporiferous zones are slightly Fig. 24.—Clypeaster crassus Kier, new species: Adapical and adoral views 648176, from Intracoastal Waterway Canal about 5 miles southwestof Little River, Horry County, S. C, X i- Basicoronal plate sutures not visible. 32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I45 Cooke (1959, p. 36) referred his specimens of this species fromSouth Carolina to Clypeaster subdepressus Gray. However, C. cras-sus has a much thicker margin and the area between its margin andthe ends of its petals is flat or depressed whereas it slopes marginallyin C. subdepressus. In C. crassus petal III is more widely open andnot as long relative to the other petals, and the test is less elongateand smaller. Occurrence.—Florida, Tamiami formation, loc. 9, 10. South Caro-lina, 18759, Intracoastal Waterway canal miles south-west of highway bridge near Nixons Crossroads, about 15 milesnortheast of Myrtle Beach. Types.—Holotype 648142, loc. 9;
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Keywords: ., bookauthorsm, bookcentury1800, bookdecade1860, booksubjectscience
