PLATE LIII. 
Nyassa recta. 
Page 356. 
Figs. 1-6. A series of specimens illustrating this species in its gradation of size and modification of form. 
Hamilton group. Schoharie Co., N. Y. 
Nyassa A11GUTA. 
Page 354. 
Fig-. 7. A cast of the right valve of ordinary form, enlarged to show muscular impression and cardinal line. 
Hamilton group. Pitcher springs, Chenango, Co., N. Y. 
Fig. 8. A gutta-percha impression from the same. 
Figs. 9-11. Three left valves. 
Figs. 12, 13. Two right valves of this species. 
Fig. 14. The cast of the interior of a right valve. 
Hamilton group. Pratt's falls, N. Y. 
Fig-. 15. The cast of the right valve showing muscular scars, pallial line and hinge characters. 
Hamilton group. Pratt's falls, N. Y. 
Fig. 16. A gutta-percha impression from the preceding. 
Fig. 17. A cast of a right valve of an unusually large individual. 
Hamilton group. Otsego Co., N. Y. 
Fig. 18. A gutta-percha impression from the preceding specimen. 
Fig. 19. A portion of the hinge of the same greatly enlarged. 
Fig. 20. A cast of a right valve, showing a strong anterior muscular scar, pallial line and cardinal folds 
beneath the beak. 
Hamilton group. Otsego Co., N. Y. 
Nyassa subalata. 
Page 355. 
Figs. 21-25. Right and left valves, showing the usual variety of form, the anterior muscular scar and 
pallial line. 
Hamilton group. Schoharie Co., N. Y. 
Fig. 26. A smaller left valve which has developed distinct radii upon the posterior slope. 
Hamilton group. Fultonliam, Schoharie Co., N. Y. 
