NO. 3 CASSIDULOID ECHINOIDS — KIER 163 



to be an important character worthy of generic distinction, but the 

 absence of the naked area is significant. Unfortunately, I have been 

 unable to study any specimens of their two species, and Duncan and 

 Sladen do not figure well the adoral surfaces of either species. Until 

 this area has been reexamined, it seems best to consider this genus 

 tentatively as a synonym of Rhynchopygus. Lambert {in Besairie and 

 Lambert, 1930, p. 114) describes another Paralampas, P. besairici, 

 but again his figures do not clearly show this median zone, Fischer 

 (195 1, pp. 69, 71) refers Rhyncholampas lyelli (Conrad) and Rhyn- 

 cholampas glohosus (Fischer) to Paralampas, and considers Para- 

 lampas as a subgenus of Cassidulus. Both of these species, however, 

 have a naked medial zone adorally, and should be referred to 

 Rhyncholampas. 



Synonym of RHYNCHOPYGUS 



Procassidulns Lambert, 1918. Mem. Soc. Acad. Aube, ser. 3, vol. 55, p. 33. 

 Type species by original designation, Echinites lapiscancri Leske. 



DESCRIPTION OF TYPE SPECIES 



RHYNCHOPYGUS LAPISCANCRI (Leske) 

 Plate 24, figures 5-8; text figures 135, 136 



Echinites lapis-cancri Leske, 1778. Klein's Naturalis dispositio echinodermatum, 

 p. 256, pi. 43, figs. ID, II. 



Material. — Fifty-two specimens studied in the U. S. National 

 Museum. 



Shape. — Small, elongate, smoothly rounded anterior margin, pointed 

 posterior margin, flattened adoral surface, greatest width posterior 

 to center, greatest height at center, oblique posterior face. 



Apical system. — Tetrabasal (text fig. 135), anterior, madreporite 

 extending posteriorly separating posterior genital and ocular plates. 



Ambulacra. — Petals of unequal length, petal III the longest, ex- 

 tending over two-thirds distance to margin, petals II and IV over 

 one-half, petals V and I the shortest, less than one-half ; pores con- 

 jugate, outer pore slightly elongated transversely; interporiferous 

 zones twice width of poriferous zones at greatest width ; petals closing 

 distally. 



Periproct. — Supramarginal, midway between apical system and 

 posterior margin, oval, slightly elongated longitudinally ; slight groove 

 extending posteriorly. 



Peristome. — Anterior, pentagonal, higher than wide. 



