NO. 3 CASSIDULOID ECHINOIDS — KIER 223 



Genus APATOPYGUS Hawkins 



Apalopygiis Hawkins, 1920b. Geol. Mag., vol. 57, pp. 393-401. Type species by 

 original designation, Niicleolites reccns M. Edwards. 



GENERIC DESCRIPTION 



Medium size, low, apical system tetrabasal in young, monobasal 

 in adults, four genital pores; petals narrow, open, pores conjugate; 

 "Pyrinid" plating in ambulacra beyond petals ; periproct supramar- 

 ginal, in groove extending to posterior margin ; peristome, low, not 

 pentagonal ; bourrelets slightly developed ; phyllodes single pored, not 

 widened, with two series of pores in each half-ambulacrum ; no 

 buccal pores ; no naked, granular zone in interambulacrum 5 adorally. 



Comparison with other genera. — Apatopygns resembles in general 

 appearance Niicleolites having a supramarginal periproct and simi- 

 larly shaped test, but differs in having single pores in the ambulacral 

 plate beyond the petals, in having a monobasal apical system in the 

 adults, and in having "Pyrinid" pkiting in the ambulacra beyond the 

 ambitus. Hawkins placed his genus in the Nucleolitidae, but these 

 differences seem of too great significance to permit Nucleolites and 

 Apatopygns to be included in the same family. Apatopygus is so 

 different from any other genus of the Cassiduloida that it seems 

 advisable to erect a new family for it. I was able to study a specimen 

 of the type species in the Museum of Comparative Zoology, Harvard, 

 and include photographs (pi. 34, figs. 4-7), and a drawing of its 

 phyllodes (text fig. 182). As Mortensen (1922, p. 184), Brighton 

 (1929), and Hawkins have given excellent descriptions of this species, 

 no description is included herein. 



INCERTAE SEDIS 

 Genus ASTROPYGAULUS Checchia-Rispoli 



Astropygaulus Checchia-Rispoli, 1945. Boll. Ufficio Geol. d'ltalia, vol. 68, p. 2. 

 Type species by monotypy, Astropygaulus trigouopygus Checchia-Rispoli. 



Remarks. — This genus is based on a fragment of one specimen, 

 and it is not possible to know all the characters of the type species. 

 The test is low, wide, with wide, closed petals and resembles very 

 much Pygnrus. The peristome, however, is oblique, and because of 

 this, Checchia-Rispoli considered the genus most similar to Pygaidus. 

 An oblique peristome also occurs in Pygorhynchus, and this species 

 seems more closely related to that genus. However, not enough is 

 known of this genus to permit definite assignment to any family, 

 and it seems advisable to place it in incertae sedis. 



