328 MOLLUSCA, BRYOZOA, SPONGES. 



Fig. 308. Fig. 309. 



[Oh. XVII. 



Inoceramus LamarcJcii. 

 Syn. CaUllus LamarcJcii. 

 "White chalk. (Dixon's Geol. Sussex, 

 Tab. 28, fig. 29.) 



Ostrea vesicularis. Syn. Gryphcea globosa. 

 Upper chalk and Upper Greensand. 



Fig. 310. 



Fig. 311 



Ostrea colrwrriba. 

 Syn. Gryphcea columbc 

 Upper Greensand. ' 



Ostrea carinata. Chalk marl, Upper and 

 Lower Greensand. 





Fiar. 312. 



Fig. 313. 



Fig. 314. 



Radiolites llortoni. Mantell. Houghton, 



Diameter one-seventh nat. size, 



Fig. 815. 



White chalk. 



Fig. 312. Two individuals deprived of their upper valves, adhering together. 



313. Same seen from above. 



314. Transverse section of part of the wall of the shell, magnified to show the structure. 



315. Vertical section of the same. 



On the side where the shell is thinnest, there is one external furrow and corresponding inter- 

 nal ridge, o, 5, figs. 312, 313 ; but they are usually less prominent than in these figures. This 

 species was first referred by Mantell to Jlippurites, afterwards to the genus Radiolites. I have 

 never seen the upper valve. The specimen above figured was discovered by the late Mr. Dixon, 





