CLASS I 



ECHINOIDEA 



273 



(a) Rhahdocidaris Desor (Figs. 381, 382). Test large and swollen. Poriferous areas wider 

 than in Oidaris, the two pores of a pair being distant and conjugated. A7nb in general 

 straight. Tubercles large, strongly crenulated, and more numerous than in Cidaris. Spines 

 very stout, some cylindrical or prismatic, often spiniferous. Chiefly Jura and Cretaceous ; 

 less common in Tertiary and Recent. 



Pi(i. 379. 



Eucidaris tribulo'ides (Lam.). Repent. Enlarged view of base of the 

 test and peristome, showing plated covering of the latter. 



Cidarid spines. A, 

 C. alnta Ag. B, C. 

 dorsnta Braun. Trias ; 

 St. Cassian, Tyrol. 

 C, (-'. fioriiicmiiiii Phill. 



Fifi. 381. 



RhididocUJarh nrhignyaiia Desor. Upper 

 Jura; Kelheim-Winzer, Bavaria. ^, Fiag- 

 ment of test, Vi. L', Amb plates enlarged. 



Fi(!. 382. 



Rhahdocidaris horridn 

 Merian. Middle Jura. 

 Spine, i/i- 



(b) Lciocidaris Desor. Like the preceding, but with uncrenulated tubercles. Spines 

 large, smooth, cylindrical. Cretaceous to Recent. 



(c) Stephanocidaris A. Ag. Test thin ; ajiical system larger than the peristome, the 

 plates feebly united. Recent. 



(d) Phyllacanthus Brandt. Test large, swollen, and with eight to eleven lAmh plates 

 in a column. Amh broad, pores conjugated. Primary tubercles large, smooth. Recent. 



(e) Porocidaris Desor (Fig. 383). Arab broad and straight ; pores wide ajiart, conjugated. 

 Primary tubercles perforate and crenulate. Scrobicules transversely oval, with shallow 

 grooves radiating from the periphery toward the centre, with or without pores at the outer 

 extremity of the grooves. Tertiary and Recent. 



(/) Goniocidaris Desor. Test high, with numerous coronal plates, and narrow Amb. 

 The median sutural regions of both areas are sunken, forming with the horizontal sutures 

 a zigzag, with pit-like depressions at the angles. Recent. 



VOL. I T 



