PLATE 18. 



Page 



Fig. 1 a - i. Strophodonta vaeisteiata, var. aeata. 188 



1 a- d. Ventral valves of several specimens where the shell is more or less exfoliated , the last 

 one being almost free from adhering shell. 



1 e,f, g. Profile vievps, showing the convexity of several individuals. 



1 h. The surface showing the ridges and striaj. 



1 t. A portion of a cast of the interior, which preserves the ridges, but shows no intermediate 

 striae. 



Fig. 2. Lept^na concava. 197 



2 a, b. Ventral and dorsal views of a specimen of this species. 

 2 c, d. Profile and cardinal views. 



2 e. Enlargement of area, foramen, etc. 



2/. Enlargement of the surface, showing the finer longitudinal and concentric stria?. 



Fig. 3. Strophomena radiata. 193 



3 a. The ventral valve. 



3 b, c, d, e. Casts of specimens of this species. 



