PLATE 8 

 Spirifer concinnus Hall 



Page 39 



i, 2 Cardinal views of the ventral valve, showing the deltidium (fig. 2, 



x i^O 



3 A young shell x 2, showing the concentric fimbriations 



4 A small dorsal valve 

 5-12 Views of adult shells 



13, 1 6 Enlargements of the surface of the cardinal area and its character- 

 istic sculpture 



14 Internal cast of a ventral valve 



1 5 The external surface enlarged to show the finely fimbriate surface in 



the adult condition, x 5 



Spirifer perlamellosus Hall 



Page 40 



17 Exterior of a ventral valve 



1 8 The fimbriate surface, x 10 



19 A small ventral valve 



20 Cardinal view of an adult shell 



Stropheodonta varistriata Conrad 



Page 43 



2 1 A small shell, essentially a cast of the exterior of the dorsal valve but 



retaining the shell at the beak, x 3 



22 A small ventral valve x 3 



23, 24 Somewhat exfoliated interiors of dorsal valves 



182 



