PLATE 15. 



Page 



Fijj;. 1. Orthis assimilis. 175 



I a - d. Ventral, dorsal, profile, and front views of a small specimen. 



1 e. Cast of tlie ventral valve of a larger individual, showing the vascnlar :inil nuisculiir Im- 

 pressions. 



Fig. 2. Orthis multistriata. 17t5 



2 a, b, c. Dorsal, ventral and profile views of a very symmetrical specimen of niedinm size. 



2 d, e. Front and profile views of a larger individual. 



If. Cardinal view. 



2 g, ft. i. Dorsal, ventral, and profile views of a large individual. 



2 k. Cast of ventral valve. 



2 I. Cast of dorsal valve of 2 fc. 



2 m, n. Front and profile view of the preceding specimen. 



2 0, p. Casts of dorsal valves, showing muscular and vascular impressions. 



2 r. Cast of ventral valve of a full-grown individual. 



2 », t. Front and profile view of the preceding. 



Fig. 3. Orthis depormis. 174 



3 a. View of the dorsal valve and area of the ventral valve. 



8 4. Ventral valve of the same specimen, showing the contracted and distorted beak. 



