NO. 3 CASSIDULOID ECHINOIDS — KIER 59 



studied in the Museum d'Histoire Naturelle, Geneve, Switzerland, 

 not single pored as typical in Nucleopygus. 



Range and distribution. — Middle Jurassic (Bajocian) to Cretaceous 

 (Cenomanian) of Europe and North Africa. Lambert and Thiery 

 (1921, pp. 343-346) refer many Cenomanian and post-Cenomanian 

 species to Nucleolitcs, Echinohrissus (an objective synonym of 

 Nucleolites) , and Clitopygus (herein considered a subjective synonym 

 of Nucleolites). Most of these species and probably all the post- 

 Cenomanian species belong to other genera. Among these species, 

 Fourtau's Echinohrissus ammonis and E. lefehvrei from the Turonian 

 have single-pored phyllodes and broad petals and are herein referred 

 to Petalohrissus (see p. 123 for a redescription of these two species). 

 Clark's Echinohrissus expansus according to Cooke (1953, p. 13) 

 is based on a specimen of Nucleolites scutatus from the Jurassic of 

 Europe. Lambert's Clitopygus marticensis from the Santonian has 

 single-pored phyllodes and probably should be referred to Rhyn- 

 chopygus. The phyllodes have never been figured in any of the other 

 post-Cenomanian species that Lambert and Thiery refer to Clitopygus, 

 but it is probable that they are all single pored and that the species 

 should be referred to other genera. Ikins' (1940, p. 28) Nucleolites 

 zvilderac from the Senonian is, according to Cooke (1953, p. 17), 

 conspecific with the Texan specimens of Weisbord's (1934, p. 191) 

 Echinohrissus cubensis, which is herein (p. 122) considered a 

 Petalohrissus. 



I have seen specimens of Peron and Gauthier's Echinohrissus 

 rotundus in the Lambert Collection and include a photograph of one 

 of them (pi. 7, fig. 7). It has double-pored phyllodes (text fig. 41) 

 and is the latest occurring Nucleolites (Cenomanian) that I have seen. 



DESCRIPTION OF TYPE SPECIES 



NUCLEOLITES SCUTATUS Lamarck 

 Plate 6, figures 1-.3; text figures 30-.32, 49 

 Nucleolites scutatus Lamarck, 1816. Aniuiaux sans vertebres, vol. 3, p. 36. 



Material. — Fifty specimens studied in the U. S. National Museum. 



Shape. — Small to medium size, subquadrangular in marginal out- 

 line, expanding posteriorly, with greatest width posterior to center, 

 anterior margin smoothly rounded, posterior indented at anal groove ; 

 adapically inflated, with thick margins, sides sloping steeply ; adorally 

 pulvinate with ambulacra slightly depressed, peristome very depressed. 



Apical system. — Anterior, tetrabasal (text figs. 30-32), genital 2 



