NO. 3 CASSIDULOID ECHINOIDS — KIER 8/ 



Apical system. — Very eccentric anteriorly, four genital pores, tetra- 

 basal, posterior genital plates separated by genital 2. 



Ambulacra. — Petals open, long, extending almost to margin, pos- 

 terior petals longer than others; poriferous zones narrow, tapering 

 distally, one-half width of interporiferous zones; pores strongly con- 

 jugate, outer pore of pair elongated transversely, inner round. 



Periproct. — Marginal, slightly visible from above, elongated longi- 

 tudinally. 



Peristome. — Large, anterior, depressed, oblique with long axis ex- 

 tending from posterior right to anterior left. 



Floscelle. — Bourrelets slightly developed; phyllodes (text fig. 71) 

 slightly broadened, depressed, double pored with two series of pore 

 pairs in each half -ambulacrum : eight pore pairs in each outer series, 

 four or five in each inner; no buccal pores. 



Occurrence. — Cretaceous (Cenomanian) of Algeria and Tunisia. 



Location of type specimen. — According to Cotteau, the type speci- 

 men is in the Coquand Collection, 



Remarks. — The figures of Pygopistes coquandi in Cotteau, Peron, 

 and Gauthier (1879, P^- ^^y %s. 7-12) are not accurate. They show 

 a test with a symmetrical marginal outline, whereas the right anterior 

 margin projects more anteriorly than the left. Furthermore, the 

 apical system is depicted as being almost central, whereas it is very 

 eccentric anteriorly, and the periproct is shown to be lower than it 

 really is. Perhaps because of these inaccuracies, Gauthier (1889a, 

 p. 36) erected a new species, Pygopistes excentricus for specimens 

 that are herein believed to be conspecific with P. coquandi. Gauthier's 

 lectotype (herein designated) is in the Museum National d'Histoire 

 Naturelle, Paris. I include photographs of it (pi. 13, figs. 4-6). In 

 Gauthier's figure he shows the periproct far more anterior than it 

 really is. 



Genus HYPOPYGURUS Gauthier 



Hypopygurus Gautliier, 1889a. Ech. foss., Tunis ie, pp. 37, 38. Type species by 

 monotypy, Hypopygurus gaudryi Gauthier. 



GENERIC DESCRIPTION 



Medium to large, low, elongate with pointed posterior margin, adoral 

 surface concave ; apical system anterior, tetrabasal with four genital 

 pores ; petals broad, open, with straight poriferous zones, petals I 

 and V longer than others, pores conjugate, outer pore slitlike, all 

 ambulacral plates double pored; periproct inframarginal, elongate 



