304 



MISS MCDONALD A^'D DE. TEl'EMAX OX [vol. IxXviL 



Fig. 4. — Diagram ilhistrating the (iccelercdion of development 

 in tliree related gastropods of tlie Proceritliium cf. slatteri 

 qroup. 



G=3 



11. 



111. 



IV. 



VI. 



VI 1. 



Vlll. 



11. 



111. 



IV. 



V. 



VI. 



Vll. 



Vlll. 



IX. 



IX. 



X. 



X. 



ei=Procerit'hiiim sp.. Lower Lias (hirchi zone), Shekill's Brickyard, Peb-^vortb 

 (Gloucestershire). L. Richardson coll. L.G. 59. 



'h=Proceritliiv.m sp., Lower Lias, tunnel-heaps. Old Dalbj (Leicestershire). 

 L. Eichardson coll. L.G. 13. 



cz^Proceriiliium cf. slatteri (Tate), Lower Lias {jamesoni zone), railway- 

 cutting, Toddington (Gloucestershire). L. Eichardson coll. L.G. 19. 



[The Eoman numerals denote the number of the whorl from the apex.] 



