PLATE 7. 



Page 

 Fig. 1. OrTHIS 80LITAEI a 45 



1 o. Dorsal view of the specimen described. 

 1 6. Ventral view of the same. 

 1 e. Profile of the same. 



1 d. Front view of the same. 



Figs. 2, 3. Orthis ctclas 52 



2 a. Dorsal view of a specimen enlarged to two diameters. 

 2 6. Ventral view of the same. 



8. A ventral valve enlarged to two diameters. 



Fig. 4. Orthis lkucosia 48 



i 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 int«rior of a dorsal valve. 

 4 h. The interior of a ventral valve. 



4 t. A cast of a ventral valve which is probably of this species, iVom Cumberland, Ud. 



Fig. 5. Orthis tulliensis 55 



6 a. Dorsal view of a specimen of ordinary size. 



6 b. Ventral view of the same. 



6 c. Profile of the same. 



6 d. Cardinal view of the same. 



5 e. Front view of the same. 



6 f. Ventral view of a more gibbous specimen. 



5 g. Profile of the same. 



6 h. Front view of the same. 



6 i. Dorsal view of a cast of this species. 



6 k. Ventral view of the same.  



