170 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



Tuberculation. — Adorally tubercles considerably larger than adapi- 

 cally ; naked, pitted medial zone in interambulacrum 5. 



Occurrence. — Danian, Ungozya, Mangyshlak, Russia. 



Location of type specimen. — Geological Museum of the Academy 

 of Sciences, Leningrad, Russia. 



Genus OCHETES Pomel 



Ochetes Pomel, 1883. Class, nicth., p. 57. Type species, herein designated, 

 NuclcoUtcs morrisii Forbes. 



GENERIC DESCRIPTION 



Small, elongate, low ; apical system tetrabasal, central, four genital 

 pores ; petals slightly developed, periproct supramarginal, in deep 

 groove ; peristome anterior, pentagonal ; bourrelets well developed ; 

 phyllodes very broad, double pored with pore pairs in two series, 

 few in inner series ; no buccal pores, sphaeridia in two rows in each 

 ambulacrum ; tubercles on adoral surface large with bosses eccentric 

 anteriorly in large scrobicules ; naked, pitted area in interambulacrum 

 5, ambulacrum III. 



Comparison with other genera. — Ochetes is distinguished from 

 Nucleopygns by its less developed petals, more developed bourrelets, 

 broader, double-pored phyllodes lacking buccal pores, and much larger 

 adoral tubercles. It is easily distinguished from Nucleolites by its 

 lower test, subpetaloid petals, more developed bourrelets, and greatly 

 widened phyllodes with fewer pore pairs in the inner series. Further- 

 more, in Ochetes morrisii the tubercles on the adoral surface are 

 much larger than those on the adapical, and there is a naked, pitted 

 area in interambulacrum 5 and ambulacrum III. 



Ochetes is similar to Rhynchopygus, both genera having small, 

 low tests, slightly developed petals, tetrabasal apical systems, supra- 

 marginal periproct, and a well-developed floscelle. In both genera 

 the tubercles on the adoral surface are large, and there is a naked, 

 pitted area in interambulacrum 5 and ambulacrum III, However, 

 in Ochetes the phyllodes are double pored, whereas in Rhynchopy- 

 gus they are single, and in Ochetes the bourrelets are less pointed. 

 As both these distinguishing characters are more primitive, and 

 as Ochetes occurs in older rocks, it is probably an ancestor of 

 RhyncJwpygus. 



Remarks. — Lambert and Thiery (1921, p. 347) and Mortensen 

 (1948, p. 185) both considered Ochetes a synonym of Nitcleopygus. 

 While it is true that most of the species that Pomel referred to his 



