64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



Thigopygus Pomel, 1833. Op. cit., p. 59. Type species herein designated, Echino- 

 brissiis humilis Gauthier. 



Remarks. — Most authors have considered the above genera of 

 Pomel's as synonyms of Nucleolites. They are distinguished from 

 each other and Nucleolites on slight differences in shape, position of 

 the periproct, and length of the anal groove. These differences are 

 often variable within a single species and certainly are not of generic 

 importance. The phyllodes and petals are very similar in all these 

 "genera." I have seen specimens of all the type species except 

 Thigopygus, but do not believe that a redescription of these species 

 is justified since they are all so similar to each other. However, since 

 photographs have never been published of most of these species, nor 

 drawings of their phyllodes, I have included them herein. 



? Synonym of NUCLEOLITES 



HeteronucJcus Lambert, 1911b. Ann. Univ. Lyon, ser. i, vol. 30, p. 184. Type 

 species by original designation, Heteronuclens peroni Lambert. 



Remarks. — Lambert erected this genus because he thought that 

 ambulacrum III was not petaloid in the type species. In all other 

 respects, he considered it similar to Clitopygus (herein considered a 

 synonym of Nucleolites) . In his brief description of the holotype, 

 and only specimen of this species, he stated that the pores were 

 microscopic in ambulacrum III. I have studied this specimen and 

 have found that ambulacrum III was petaloid originally, but owing 

 to the poor preservation of the anterior area of the holotype, most 

 of this petal is missing. Three plates are present near the apical 

 system in ambulacrum III, and their pores are just as large as those 

 in the other petals. Since Lambert's description is very brief, and 

 the species has never been figured, I include below a description and 

 illustrations of the holotype. According to Lambert, the holotype is 

 from the Senonian, but I suspect from the worn appearance of the 

 specimen and the many primitive features that ally it with Nucleo- 

 lites, that it is reworked from older strata. 



DESCRIPTION OF TYPE SPECIES 



HETERONUCLEUS PERONI Lambert 

 Plate 44, figures 9-12 

 Heteronucleus peroni Lambert, op. cit., p. 184 (footnote). 



Material. — Only one specimen, the holotype, is known. This speci- 

 men is finely fractured with the test broken or worn away in many 



