SYSTEMATIC DESCRIPTIONS — CLYPEASTRINA. 45 



fossil West Indian Clypeaster, approaching nearest to C. platygaster, 

 the next-described species, but it differs from that in that platygaster 

 is perfectly flat ventrally, whereas oxybaphon is concave. C. oxybaphon 

 resembles C. reticulatus (Linnaeus) of the Indo-Pacific region in test 

 form, but has very different petals. 



Oligocene, Antigua formation, from bluff north side of Willoughby 

 Bay, Antigua, T. W. Vaughan collector, 1914; U. S. Geol. Sur. 

 station 6881, 4 specimens; the holotype, U. S. Nat. Mus. No. 328241; 

 the paratype figured in plate 8, U. S. Nat. Mus. No. 328242; and two 

 additional paratypes, U. S. Nat. Mus. No. 328243. Rifle Butts, Anti- 

 gua, T. W. Vaughan collector, 1 specimen, U. S. Geol. Sur. station 6851. 



Oligocene, cliff face, east shore Guanica Harbor, Porto Rico, 300 feet 

 south of small cave (of station 341), beds of shaly limestone somewhat 

 stratified; 8 good specimens, including those figured on plate 7, 

 figures 3 and 4, which are in the American Museum Nat. Hist. Nos. 

 18567 and 18568; also some 50 fragmentary specimens, numerous 

 stations under this locality, stations 368, 369, 371 to 375, 377, 380. 

 East shore of Guanica Harbor, Porto Rico, from small cave in Tertiary 

 limestone, dip 3° 10' south, 4 specimens, stations 341, 345, 346. White 

 gray ledge, capping top of hill, 1 km. distant and south 37° east of 

 Guanica central mill, Porto Rico, 1 good specimen and 8 fragments, 

 stations 355, 356. Juana Diaz shales, ford on Jacaguas River, 1 km. 

 northwest of Juana Diaz, Porto Rico, 4 fragments, station 185. All 

 above Porto Rican material collected by C. A. Reeds on Expedition of 

 the New York Academy of Sciences, the Porto Rican Government and 

 American Museum of Natural History cooperating. 



Clypeaster platygaster, 1 new species. 

 (Plate 9, Figures 1, 2.) 



The following is a description of this species : 



Test elongate, pentagonal, drawn out anteriorly; truncate posteriorly, 

 with thick, rounded margin. Dorsally the test is depressed in a saucer- 

 like fashion, in the middle of which the center of the test rises to a moderate 

 elevation above the outline of the thickened margin. Ventrally the test 

 is perfectly flat, a marked distinction from the preceding species, C. oxy- 

 baphon. The apical disk, which is very small, does not show structural 

 detail. It is situated almost in the center of the test, but about 3 mm. 

 nearer to the anterior border than it is to the posterior. Ambulacral petals 

 are very broad, moderately elevated above the general surface, nearly 

 closed at the tips. The petals are all of very nearly the same width, but 

 III is the longest. The posterior pair I and V are shorter and the anterior 

 pair II and IV are still shorter. The poriferous areas of the petals are very 

 wide, sunken, and strongly marked; the furrows connecting the pores are 

 deeply incised, and the ridges between bear about 10 small tubercles at 

 the widest part. The interporiferous areas are remarkably attenuated. 

 The ambulacral furrows on the ventral side are strongly marked, deepening 



1 irXctrGs flat; yatrriip belly. 



