70 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



developed, phyllodes double pored, broad, with two scries of pore 

 pairs in each half-ambulacrum ; no buccal pores. 



Comparison zmth other genera. — Duncan (1891, p. 188) consid- 

 ered Clypeopygus as only a subgenus of Clypeus, dififering from it 

 in having a more anteriorly eccentric apical system, and narrower 

 poriferous zones. However, Clypeopygus is a more advanced form 

 than Clypeus and certainly not a subgenus of it. The phyllodes of 

 Clypeopygus are broad with only two series of pore pairs with few 

 pore pairs in each, as opposed to the long, not widened phyllodes of 

 Clypeus with three series of pore pairs in each half-ambulacrum. 

 Furthermore, the peristome in Clypeopygus is very eccentric an- 

 teriorly, whereas in Clypeus it is central or only slightly anterior. 



Lambert and Thiery (1921, p. 349) consider Petalobrissus a sub- 

 genus of Clypeopygus. As Clypeopygus has double pores in its 

 phyllodes and no buccal pores, it must be considered generically 

 distinct from the more advanced Petalobrissus which has single pores 

 in its phyllodes and buccal pores. Lambert and Thiery were not 

 aware of these differences. In addition to these differences, Clype- 

 opygus is much more depressed than Petalobrissus. 



Clypeopygus is most similar to Nucleolites, both genera having 

 similar petals, phyllodes, and periproct. They differ only in that the 

 test is more depressed in Clypeopygus. 



Lambert and Thiery refer many species to this genus. As I have 

 discussed on page 120, few of the post-Cenomanian species, perhaps 

 none of them, belong to this genus. Among the pre-Cenomanian and 

 Cenomanian species, Clark's Echinobrissus angustatus has single- 

 pored phyllodes with very few pores, buccal pores, slightly developed 

 phyllodes, and a high test, and is herein referred to Nucleopygus 

 (see p. 167). Nucleolites subquadratus Agassiz is too inflated for 

 Clypeopygus, and should be referred to Nucleolites (see p. 63). 



Weisbord (1934, p. 32) provisionally referred an Upper Creta- 

 ceous species to Clypeopygus, C. habanensis. I believe, however, that 

 this species should be referred to Hardouinia. I have studied his 

 holotype and found single-pored phyllodes. The shape of the test, 

 and location and shape of the periproct is very similar to Hardouinia. 

 Of even greater significance, its genital plates are greatly elongated, 

 extending between the petals, a character typical in Hardouinia. 



Range and distribution. — Cretaceous (Neocomian-Cenomanian) 

 of Europe and Africa. 



