^'0- 3 CASSIDULOID ECHINOIDS KIER 1 59 



Range.— Lower Cretaceous (Albian) to Recent. 



Comparison with other genera.— The Cassidulidae are most similar 

 to the Xucleolitidae, from which they differ in having more developed 

 bourrelets, wider phyllodes with fewer pores, a naked, often pitted 

 zone adorally in interambulacnim 5, and larger tubercles adorally. 



Genus RHYNCHOPYGUS d'Orbigny 



Rhynchopygus d'Orbigny, 1856. PaL franc, Cretace, vol. 6, p. 323. Type species 

 by virtual monotypy, Cassidulus marmini Agassiz. d'Orbigny referred another 

 species to this genus, but since he questioned whether it really belonged to 

 the genus, it is not available as type species. 



Synonyms : ? Paralampas Duncan and Sladen ; Procassidulus Lambert. 



GENERIC DESCRIPTION 



Small, low, oval, or with greatest width posterior to center, anterior 

 margin smoothly rounded, posterior often pointed, anterior adapical 

 surface gently curved, posterior often truncated obliquely; adoral 

 surface flat; apical system anterior, tetrabasal, four genital pores; 

 petals shghtly or well developed, equal or with ambulacrum III 

 longer than others, open or closing distally, conjugate pores, am- 

 bulacral plates beyond petals with single pores; periproct supra- 

 marginal, transverse or longitudinal, groove extending from opening 

 to posterior margin ; peristome, central to anterior, circular to oval ; 

 bourrelets well developed, often pointed; phyllodes widened, single 

 pored, with slight crowding, only few pores occluded ; buccal pores 

 present; tubercles adorally much larger; naked, often pitted, median 

 area in interambulacrum 5, ambulacrum III. 



Comparison with other genera. — Rhynchopygus is very similar to 

 Cassidulus but differs in having a tetrabasal apical system. It is 



Figs. 128-136. — 128, GentUia tafileltensis ? Lambert: Phyllode of ambula- 

 crum IV of specimen in the Lambert Collection, Sorbonne, Paris, probably from 

 the Cretaceous (Cenomanian) at Riz el Abiod, X 10. 129-131, GentUia syriensis 

 Kier: 129, Phyllode of ambulacrum IV of specimen in Museum National 

 d'Histoire Naturelle, Paris, from Cretaceous (Cenomanian) of Syria, X 10 ; 

 130, enlarged view of adoral portion of same phyllode showing minute buccal 

 pores, X15; ^3i> view of left poriferous zone of ambulacrum III adoral to 

 petaloid portion showing arrangement of pores into two series, on same speci- 

 men as figure 130, X 20. 132, 133, Rhynchopygus lusitanicus (De LoriolJ : 132, 

 Phyllode of ambulacrum V of USNM 131264, from the Upper Cretaceous 

 (Lower Turonian) at Pougnadoresses (Gard), France, X 20; 133, apical system 

 of same specimen, X 20. 134? Rhynchopygus marmini (Agassiz) : Apical system 

 of USXil 19559, from the Upper Cretaceous (Senonian) at Port Brehay, 

 Manche, France, X 15- i35. 136, Rhynchopygus lapiscancri (Leske) : 135, Apical 

 system of USN^I 131263, from the Upper Cretaceous (Maestrichtian) at 

 St. Pietersberg, Belgium, X15; 136, phyllode of ambulacrum V of USNM 

 131260, from the Upper Cretaceous (Maestrichtian) at Beeringen (Charb.), 

 Belgium, X I5- 



