NO. 3 CASSIDULOID ECHINOIDS — KIER 97 



Shape. — Small, holotype ii mm. long, topotype 15 mm., elongate, 

 with smooth marginal outline except for slight posterior truncation; 

 adapical surface highly inflated, with steep sides, greatest height 

 posterior to center; adoral surface flattened, peristome flush. 



Apical system. — Anterior (text fig. 79), tetrabasal, four genital 

 pores. 



Ambulacra. — All ambulacra petaloid, petals narrow, very short, 

 perhaps reflecting immaturity of specimens. Details of pores not 

 visible. 



Periproct. — Marginal, in center of posterior truncation. 



Peristome. — Anterior, pentagonal. 



F/oJc^//^.— Bourrelets with vertical sides. Phyllodes definitely 

 developed with slight crowding of single pores; buccal pores present 

 (text fig. 80). 



Occurrence. — Upper Cretaceous (Campanian) of Roiz (Santen- 

 der), Spain. 



Remarks. — Lambert believed that ambulacrum III was nonpetaloid 

 in the type species of his Pseudonucleiis. If this was so, then he was 

 justified in erecting a new genus for it. However, I have studied 

 under high magnification the holotype and one topotype in his collec- 

 tion and found that ambulacrum III is petaloid. In the holotype, 

 the area where ambulacrum III occurs is badly eroded, and if it had 

 been petaloid, there would have been no way to have known it. In a 

 second topotypic specimen, ambulacrum III is definitely petaloid, and 

 there is no question that this specimen is conspecific with the holotype. 

 Lambert does not mention this second specimen in his description and 

 it is possible that he received it after describing this species. In his 

 original description Lambert states that the pores are not conjugate 

 in the petals, but Lambert and Thiery (1921, p. 358) say that they are 

 conjugate. The specimens are so badly weathered and details of the 

 test so obscured by secondary growth that I was unable to discern 

 whether they were conjugate or not, 



Lambert considered this species similar, except for its ambulacrum 

 III, to Oolopygus or Catopygus. In its shape with its smoothly 

 elongate, highly inflated test, it is very similar to Oolopygus. It is 

 similar in having its apical system very eccentric anteriorly, in its 

 inconspicuous petals and location of its periproct. Unfortunately, 

 the two and only known specimens of Pseudonucleus are very small 

 and may show immature characters. It therefore seems advisable to 

 consider Pseudonucleus only tentatively as a synonym of Oolopygus. 



