230 ECHINODERMATA—ECHINOIDEA SUB-BRANCH IIT 
extended into the depressed posterior [4mb. Pairs of basal plates separated 
by the antero-lateral radials, the fifth basal absent. Cretaceous. HH. libycum, 
Cotteau. 
Codiopsis, Ag. (Fig. 369). Primary tubercles of both areas small, smooth, 
nearly equal in size, and only occurring actinally and for a short distance 
toward the ambitus. Pairs of pores uniserial. Cretaceous. 
Cottaldia, Desor. Cretaceous and (?) Recent. Plewrodiadema, de Loriol. 
Jura. Magnosia, Michelin. Jura and Cretaceous. 
Sub-Family B. DrpLopoprinae. 
Ambulacral plates compound ; pairs of pores biserial. 
Diplopodia, M‘Coy. Amb narrow, with two vertical rows of perforate and 
crenulate primary tubercles. Pairs of pores in double vertical series near the 
poles, uniserial at the ambitus. Jura and Cretaceous. 
Pedinopsis, Cotteau. Cretaceous. Phymechinus, Desor. Jura. 
Sub-Family C. PEDININAE. 
Ambulacral plates compound ; pairs of pores triserial. 
Pedina, Ag. Amb narrow, poriferous zones wide. Both areas with two 
vertical rows of small, perforate, primary tubercles. Upper Jura. 
Pseudopedina, Cott. Like the preceding, but with larger primary 

Fia. 370. 
_ Stomechinus lineatus, Goldf. sp. Coral Rag; Sontheim, Wurtemberg. 4, Side-view of test, 1/}. B, Portion 
of actinal surface. 
tubercles, which are present in the Amb near the ambitus only. Upper 
Jura. 
Micropedina, Cott. Amb with several, and L4mb with numerous vertical 
rows of very small primary tubercles. Cretaceous. 
Stomechinus, Desor (Fig. 370). Distinguished from Pedina by its wider 
Amb, and imperforate, non-crenulate, primary tubercules. Secondary 
tubercles and granules often present. Jura and Cretaceous. 
Codechinus, Desor. Tubercles very small, plain, irregularly distributed. 
Cretaceous. 
Polycyphus, Ag. Jura. Astropyga, Gray. Recent. 
