CLASS I 



ECHINOIDEA 



27' 



primordial ambulacral, also non-amhulacral plates. Lantern 

 indined. Stewarts organs slight, or absent. Lias to Recent. 



Centreehinus Jackson {Diadema Schynvoet) (Fig. 368, 

 narrow, often projecting; two vertical 

 rows of small, primary, crenulate and 

 perforate tubercles extending from 

 peristome to apex. IAr)ih with two 

 or more vertical rows of primary 

 tubercles resembling those of the 

 Amb, but larger. Secondary tubercles 

 and granules surrounding the scrobi- 

 cules. Spines long, hollow, longitu- 

 dinally striated. Lias to Recent. 



Hemipedina AVright. Jura, Creta- 

 ceous and Recent. Differs from Centre- 

 ehinus in having simple Amb plates 

 near the apex, and perforate, but 

 not crenulate tubercles. 



Pseudodiadema Desor (Fig. 388). 

 Includes small species having wide 

 Amb, tubercles of uniform size in 

 Amb and lAmb areas, and oculars 

 typically all exsert. Jura to Ter- 

 tiary. 



Heterodiadema Cotteau. Like 

 Centreehinus, but with the apical 

 System greatly extended into the depressed posterior 

 H. libycum Cotteau. 



erect, or (Astropijga) 

 D). The Amh are 



Pseudodiaclenm neglectum 

 Jura. A, B, Profile and 

 C, Ambulacrum, enlarged.' 



Thurm. Froin the Bernese 

 ventral aspect of test, Vi- 

 D, Spine, V-i- 



lAmb. Cretaceous. 



Codiopsis Ag. (Fig. 389). Primary tubercles of both areas small, smooth. 



Fig. 389. 



Codiopsis dovia (Desin.). Cenonianian (Tourtia) ; Tournay, Belgium. A, Sirle-view of test, Vi- -R, Ventral 



aspect of sanie. C, Apical systein, enlarged. 



nearly equal in size, and only occurring actinally and for a short distance 

 toward the ambitus. Pore-pairs uniserial. Cretaceous. 



Cottaldia Desor. Cretaceous and (?) Recent. Fleurodiadema de Loriol. 

 Jura. Magnosia Michelin. Jura and Cretaceous. 



Diplopodia M'Coy. Amb narrow, with two vertical rows of perforate and 

 crenulate primary tubercles. Pore-pairs in double vertical series near the 

 ])oles, uniserial at the ambitus. Jura and Cretaceous. 



Fedinopsis Cotteau. Cretaceous. Phi/mechinus Desor. Jura. 



