CLASS I 



ECHINOIDEA 



293 



oblique toward the ambitus, where they are more distant. Posterior Amb 

 actinally long and broad, the pairs small, and pores oblique. Peristome oval, 

 broader than long. Periproct 

 infra -marginal, posterior, oval. 

 Apical system elongate. Very 

 abundant in the Upper Cretac- 

 eous. A. ovata (Leske) often 

 attains a very large size. 



Holaster Ag. (Fig. 415). Test 

 ovoid in marginal outline, flat 

 actinally, tumid and high abac- 

 tinally. Anterior Amb in a shal- 

 low groove. Peristome elliptical, 

 broadest transversely. Periproct 

 supra-marginal, and oval. Apical 

 system elongate. Cretaceous 

 and Miocene. 



Offaster Desor. Test small, 

 tumid. Anterior Amb sometimes 

 in a shallow groove. Peristome 

 oval, broadest transversely. Peri- 

 proct supra-marginalj circular or 

 ovoid. Apical system elongate. 

 Cretaceous. 0. pilula (Ag.). 



Hemipneustes Ag. Test large, 



ovoid in marginal outline, high Ananchytes ovata (Leske). White chalk; Haldeni, West- 

 1 . •■! 1 n a *. „*.,-„„li„ phalia. ^, B, Profile and ventral view. Vs- C, Apical system, 



and tumid dorsally, flat actinally. Enlarged. i>, Portion oiAmb and lAmb areas, i/i- 



Anterior Amb in a deep, narrow 



groove extending to the elongate apical system, its pairs of pores numerous 



D 



Fio. 414. 



Fig. 415. 

 A, B, Holaster suhglohosus Ag. Cenomanian ; Rouen, i/j. C, H. siiborbieulnrisBefT. Apical system, enlarged. 



and small, the vertical rows wide apart. Paired Amb more or less cvirved, 

 open distally, with dissimilar pores. Peristome much sunken, crescent- 



