GENERA AND GEOUPS OB" THE BCHINOlDEA. 179 



Genera incertce sedis. 

 Genus Desorella. 

 Oviclypeus. 



Genus Desorella, Gotteau, 1862, Bev. et Mag. de Zool. (pars) ; 

 and 1867-74, Pal. Frang., Ech. terr. Jura^ ix. p. 384. 



Test of moderate size, subcircular in undulating ambital out- 

 line, subconical dorsally, pulnnate actiually. 



Apical system absent, leaving a large scar ; probably a large 

 madreporite separated the posterior radial plates. 



Ambulacra with simple pairs of pores, not doubling near the 

 peristome. 



Peristome subdecagonal, oblique or not, sunken. Periproct 

 elongate, just supramarginal, large, pyriform, distant from the 

 apical system. 



Fossil. OoKte: Euroj)e. 



This is now a very unsatisfactory genus, and it formerly in- 

 cluded Pseudodesorella, which is a well-defined genus. It has 

 been determined from casts of species. 



G-enus Oyicltpeus, Dames, 1877, PalceontograpMca, Cassel, Bd. 

 XXV., Fch. Vicent. u. Veron. Tert. p. 44. 



Test large, with an oval tumid margin, subhemispherical dor- 

 sally, slightly tumid actinally. 



Apical system slightly excentric in front, small, with four 

 genital pores. 



Ambulacra similar, with wide poriferous zones extending to 

 the ambitus and furthest apart there, diverging regularly from 

 the apex downwards, diminishing in the distance of their pores 

 at the margin of the test, showing no tendency to close. Pores 

 circular, becoming slit-shaped with distance from the apex, wide 

 apart and probably with a wide intermediate groove, lasting to 

 the narrowest part of the zone ; costse with close miliaries. In- 

 terporiferous areas narrow, with numerous small, close primary 

 tubercles, which are probably plain and scrobiculate. Actinally 

 ten grooves extend from the margin to the peristome, producing 

 the appearance of five compound grooves, each groove is a pori- 

 ferous zone ; no doubling of the pairs is seen, 



Interradia tumid, wider than the ambulacra, crowded with 

 similar small, scrobiculate, primary tubercles, some hexagonal. 



12* 



