CLASS I 



ECHINOIDEA 



293 



Posterior Amb 

 Peristome oval. 



oblique toward the ambitus, where they are more distant. 

 actinally long and broad, the pairs small, and pores oblique, 

 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-marginal, circular or 

 ovoid. Apical system elongate. 

 Cretaceous. 0. pilula (Ag.). 



Hemipneustes Ag. Test large, 

 ovoid in marginal outline, high 

 and tumid dorsally, flat actinally. 

 Anterior Amb in a deep, narrow 

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



Fig. 414. 



Ananchytes ovata (Leske). White chalk ; Haldem, West- 

 phalia. Ä, B, Profile and ventral view. 1/3. C, Apical system, 

 enlarged. D, Portion of Amb and lAmb areas. 1/1. 



Fio. 415. 

 A, B, Ilolaster suhglobosus Ag. Cenomanian ; Ronen, l/i- C, H. mhorbiciilaris Defr. Apical system, enlarged. 



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

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



