NO. 3 CASSIDULOID ECHINOIDS — KIER 95 



O. pyriformis (pi. 29, figs. 7-9) and a drawing (text fig, 78) of one 

 of its phyllodes. 



Range and distribution. — Upper Cretaceous (Senonian) of France, 

 Belgium, and Holland. Oolopygus affinis Sorignet occurs in the 

 Pisolitic limestone which some authors consider to be Montian. 



Oolopygus ivilliamsi (Clark) from the Middle Maestrichtian of 

 New Jersey may be a Catopygns. The holotype, and only known 

 specimen, is an internal cast, and it is not possible to know whether 

 or not it had single- or double-pored phyllodes. 



DESCRIPTION OF TYPE SPECIES 



OOLOPYGUS GRACILIS Lambert 

 Plate 29, figures 5, 6; text figure 77 



Oolopygus gracilis Lambert, 1909. Bull. Soc. Linn. Normandie, scr. 6, vol. 2, 

 pp. 20-21, pi. I, figs. 17-18. O. gracilis is a substitute name for Oolopygus 

 pyriformis d'Orbigny, 1856, Pal. franc., Cretace, vol. 6, atlas, pi. 977, non 

 Oolopygus pyriformis (Leske), 1778. 



Material. — I have studied and photographed Lambert's figured 

 specimen, which is in his collection in the Sorbonne, Paris. 



Shape. — Small, Lambert's specimen 23 mm. long, d'Orbigny's 

 27 mm. ; elongate, posterior margin slightly truncated in Lambert's 

 specimen, but prolonged in d'Orbigny's ; adapical surface smoothly 

 inflated, adoral surface flattened ; greatest width and height posterior 

 to center. 



Apical system. — Anterior, apparently tetrabasal although sutures 

 not clear ; tetrabasal system seen in specimen of O. pyriformis Leske, 

 a species very similar to O. gracilis. Three genital pores, no pore in 

 left anterior genital plate 3. 



Ambulacra. — Petals slightly developed, equal in length, narrow, 

 open, flush with test. Poriferous zones very narrow, one-half width 

 of interporiferous zones ; pores of pore pair equal, slightly elongated 

 transversely. 



Periproct. — Marginal, oval, longitudinal, with slight groove extend- 

 ing from opening to ventral edge of test. 



Peristome. — Anterior, depressed slightly higher than wide, pen- 

 tagonal. 



Floscelle. — Bourrelets and phyllodes strongly developed. Phyllodes 

 broad, single pored, with two series of pores in each half ambulacrum : 

 8 to 10 pores (text fig. yy) in each outer series, 2 to 4 in each inner. 

 Two rows of sphaeridia in each ambulacrum ; buccal pores present. 



