NO. 4 ECHINOIDS, TRINIDAD AND VENEZUELA — COOKE I3 



Trinidad: Bella Vista Road, Mount Moriah, San Fernando (USGS 

 8879, 9201, J. A. Bullbrook). Point Bontour (Trinidad Oil Co., 

 W. Barr). 



Venezuela: Alta Casa Nueva, north of Altagracia de Orituco, 

 Guarico. Bolivar district, Zulia (Creole Petroleum Co. 151007). 



Geologic horizon. — Late Eocene : San Fernando formation, Trini- 

 dad; Tinajitas formation, Venezuela. 



Holotype.—\JS]^M 498991. 



Figured specimen. — USNM 638625. 



Remarks. — The circular outline of OUgopygus rotundus suggests 

 Oligopygus nancci Cooke, which has proportionately longer petals, 

 smaller peristomial depression, and more acute margin. O. nancei is 

 much larger. 



Oligopygus christi Jeannet is based on one corroded, ovate indi- 

 vidual from Rio Calderas, near Los Baiios, Zamoras, Venezuela (the 

 holotype) and one nearly circular fragment from Soldado Rock, Trini- 

 dad, which probably represents Oligopygus rotundus. The figures do 

 not clearly show the diagnostic features of either specimen. Both 

 are in the Naturhistorisches Museum, Basel, Switzerland. 



OLIGOPYGUS NANCEI Cooke 

 PI. 2, figs. lO-ll 



Oligopygus nancci Cooke, 1941, Journ. Paleont., vol. 15, No. 3, p. 305, 3 text figs. 

 "iOligopygiis circiilaris Sanchez Roig, 1949, Los equinodermos fosiles de Cuba, 

 Paleontologia Cubaana, vol. i, p. 159, pi. 29, figs. 2-3. 



Test moderately large ; outline subpentagonal to subcircular, widest 

 at the anterior paired ambulacra; about half as high as long; upper 

 surface regularly convex ; lower surface nearly flat. Apical system 

 central ; four genital pores, widely separated. Petals long, not quite 

 reaching the ambitus, the anterior somewhat longer than the paired 

 petals, straight, open at the distal ends; poriferous zones nearly as 

 wide as the interporiferous zones, slightly curved inward at the tip; 

 pore pairs conjugate; inner pores nearly circular, outer pores elon- 

 gated ; pores at the ends of the plates. Extrapetalous pores in diagonal 

 pairs becoming linear near the peristome. Peristome central, rather 

 small, deeply sunken in a steep-walled, transversely elliptical pit. Peri- 

 proct round, flush, about one-third the way from the margin to the 

 peristome. Tubercles fairly large, about the same size on top and 

 bottom sides ; interscrobicular spaces densely papillatcd. 



Dimensions of holotype and figured paratype : Length 51 and 



