PLATE 19. 
Page 
ig. 1 a - y. Strophomena rugosa. 195 
ld-i. Figures illustrating the usual characters presented by shells of this species. 
1 fc ( by error marked Is). Profile showing the great extent of the deflected portion of the 
shell. Between this one and 1 b f, there are every possible gradation. 
2 & 2 f. Specimens which are slightly curved, and showing a larger number of corrugations 
than usual, which extend nearly to the base of the shell. 
1 l, m, n. Interiors of dorsal valves, showing some variety of characters. 
1 l f. Enlargement of the stria on the interior. 
1 o, p , q. Casts or moulds left in the stone by the dorsal valves of several individuals. 
1 q f. Enlargement of the muscular imprints, etc. 
1 r, s, t. Interior of the ventral valve of several individuals. 
1 u, x, y. Casts of the interior of the ventral valve, 1 u still retaining a portion of the shell. 
