Derbyina whitiorum Clarke 



Fig. 1,2 Exterior and internal cast of ventral and dorsal valves 



3 Enlargement of ventral hinge 



4 A dorsal valve 



Locality: Ponta Grossa, Brazil 



Leptocoelia flabellites (Conrad) 



Fig- 5 Exterior of an average adult specimen 



6 A dorsal valve 



7 Internal cast of large ventral valve 

 Locality: Ponta Grossa, Brazil 



8 Internal cast of dorsal valve 

 Locality: Jaguariahyva, Brazil 



9 Dorsal cast 



Locality: Cold Bokkeveld, Cape Colony 



Coelospira ? colona Clarke 



Fig. 10, II Ventral valves, x 2 



12, 13 Ventral and dorsal views, x 2 

 Locality: Ponta Grossa, Brazil 



Leptostrophia ?? mesembria Clarke 



Fig. 14 Exterior of ventral with internal cast of dorsal valve 



15 Sculpture cast showing dorsal aspect 

 Locality: Fox bay, West Falkland 



16 Enlargement of hinge structure showing incipient denti- 



cles or spinules on cardinal line 



17 Internal cast of ventral valve 

 Locality: Ponta Grossa, Brazil 



18 Internal ventral cast 

 Locality: Jaguariahyva, Brazil 



Z94 



