74 FOSSIL ECHINI OF THE WEST INDIES. 



the ambitus. Ambulacra petaloid, wide, in deep, broad furrows. The 

 anterior ambulacrum III is narrower than the others and lies in a shallow 

 furrow which reaches to the ambitus. Ambulacra II and IV, the anterior 

 pair, are widely divergent, at an angle of about 95 to each other and are 

 in grooves, which extend nearly to the ambitus. They measure 30 mm. 

 in length. The posterior ambulacra I and V lie in grooves and are narrower 

 and much shorter than the anterior pair, measuring about 18 mm. in length. 

 The pores in the paired ambulacra are at the ends of narrow, slit-like 

 grooves. The interambulacra are narrow and elevated dorsally. The 

 apical disk is very close to median in position, perhaps actually median, 

 but, from imperfections posteriorly, exact measurement in the antero- 

 posterior axis can not be made. The apical disk is quite well preserved 

 and shows the 4 genital plates with large perforations; the madreporite 

 is of medium size, meeting but not separating the other genitals. Oculars 



1 and V are in contact on account of the absence of genital 5, as is charac- 

 teristic of the genus. From imperfections the peristome and periproct 

 are not preserved. Small perforate tubercles with scrobicules are scattered 

 over the test somewhat distantly and small granules thickly cover the 

 spaces between the larger tubercles. 



The specimen measures 40 mm. in height, and this is a close approxima- 

 tion to the real height ; if not worn ventrally, it would be slightly higher. 

 It measures about 65 mm. in length and 65 mm. in width. This species 

 is very much larger and more conical than any other fossil species of 

 the genus from the West Indies; it differs also in its shape from any 

 known North American species. At the request of the collector, Mr. 

 Graham John Mitchell, this species is named in honor of Professor 

 Charles P. Berkey, of Columbia University. 



Cretaceous, Guanica Central, just west of the town of Guanica, South 

 coast of Porto Rico, holotype, 1 specimen, station 211. This fossil 

 echinoid, with a few other fossils, is from a dense, hard limestone from 

 the upturned and unconformable beds of the older formation, which 

 Professor Berkey 1 considers as Cretaceous. It was collected by Mr. 

 Graham John Mitchell, who had charge of the Ponce district in the 

 survey work of 1917. 



Genus PARASTER Pomel. 



Type species. Schizaster gibberulus Agassiz, 1847, Catalogue Rai- 

 sonne, Ann. Sci. Nat., ser. 3, vql. 8, p. 22. 



All of the species described by Cotteau in his St. Bartholomew and 

 Anguilla memoir as Schizaster belong properly to the genus Paraster. 

 There are no Recent species of Paraster in the West Indian region, so far 

 as we yet know. The genus Schizaster is characterized by having only 



2 genital pores, which are in genital plates 1 and 4, whereas the genus 

 Paraster has 4 genital pores, 1 in each of the genital plates existent. 

 Genital 5 is absent typically in both genera. 



1 Scientific Survey of Porto Rico and the Virgin Islands. New York Acad. Sci., vol. 1, part 

 1. 1919. 



