PLATE 35 



Stropheodonta rosieri nov. 



Page no 



I, 2 Two shells showing somewhat different ontogenic progress and indi- 

 cating the relation of these mature characters toS. varistriata 

 and S. patersoni. X2 

 6V Alban beds. Cape Rosier Cove 



Stropheodonta patersoni Hall protype precedens nov. 



Page i86 



3 A young shell showing the primitive character of the surface at this 



growth stage 

 4, 5, 7 Shells showing a gradual approach to normal mature conditions 



with fine subequal radii and umbonal crenulations 

 6 Enlargement of a portion of the surface in the pallial region, showing 



alternating radii and fine concentric lines, x 5 

 8 A ventral valve showing in strong contrast the incipient, adolescent 



and mature styles of sculpture 

 9-13 Other valves each showing a difference from the rest in growth 

 phase. In figure 10, the sculpture is mature and ultimate and 

 indicates acceleration which has virtually skipped the anephebic 

 crenulations. The same expression is given by 12 which is the 

 original of Mr Billings's S . inequiradiata Hall. In 13 the 

 long continuance of the anephebic condition is particularly 

 noteworthy 

 Grande Grcvc limestone. At various localities, on the Forillon. 

 Figure 12 is from Indian Cove. 



Stropheodonta crebristriata (Conrad) protype simplex nov. 



Page 187 



14 A partially silicified ventral valve showing the character of the plica- 

 tions. X 2 



Grande Grlve limestone. Grande Greve 



322 



