PLATE LIV. 



Ptrina l^vis, Agassiz. 



From the Upper Greensand. 



Fig. 1 a. Test, upper surface, natural size. My collection. (P. 238.) 



b. Do. do. magnified two diameters. 



c. Do. under surface do. do. 



d. Do. lateral view do. do. 



e. Do. posterior view do. do. 



Pyrina Desmoulinsii, D'Archiac. 

 From the Chloritic Marl. 



Fig. 2 a. Upper surface, natural size My collection. (P. 236.) 



b. Under do. do. 



c. Lateral view do. 



d. Posterior do. do. 



e. Ambulacral and inter-ambulacral plates and poriferous zones, magnified four 



diameters. 

 /. Apical disc, highly magnified. 

 ff, h, i. Various forms of basal tubercles, highly magnified. 



Pyrina ovulum, Lamarck. 

 From the Upper Greensand. 



Fig. 3 a. Test, upper surface, natural size. Royal School of Mines. (P. 237.) 

 b. Do. do. magnified three diameters. 



c Do. under surface do. do. 



d. Do. lateral view do. do. 



e. Do. posterior do. do. do. 

 /. Apical disc, highly magnified. 



(/. Plates, tubercles, and granules, highly magnified. 

 h. Do. do. do. do. 



