PLATE 7. 
Page 
Fig. 1. Orthis solitaria. 45 
1 a. Dorsal view of the specimen described. 
1 b. Ventral view of the same. 
1 c. Profile of the same. 
1 d. Front view of the same. 
Figs. 2, 3. Orthis cyclas. 52 
2 a. Dorsal view of a specimen enlarged to two diameters. 
2 b. Ventral view of the same. 
3. A ventral valve enlarged to two diameters. 
Fig. 4. Orthis letjcosia. 
4 a. Ventral view of a small specimen. 
4 b. Dorsal view of the same. 
4 c. Dorsal view of a specimen of ordinary size. Larger specimens have been obtained since 
these figures were made. 
4 d. Ventral view of the same. 
4 e. Profile of the same. 
4/. Cardinal view of the same. 
4 g. The interior of a dorsal valve. 
4 h. The interior of a ventral valve. 
4 i. A cast of a ventral valve which is probably of this species, from Cumberland, Md. 
48 
Fig. 5. Orthis tulliensis 
5 a. Dorsal view of a specimen of ordinary size. 
5 b. Ventral view of the same. 
5 c. Profile of the same. 
5 d. Cardinal view of the same. 
6 e. Front view of the same. 
5/. Ventral view of a more gibbous specimen. 
5 g. Profile of the same. 
5 h. Front view of the same. 
5 i. Dorsal view of a cast of this species. 
5 fc. Ventral view of the same. 
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