PLATE Llll. 



^YASSA KECTA. 

 PageSSe. 

 Figs. 1-6. A series of aijecimiMis illiustrating: this species in its gradation of size and modification of fonn. 

 Hamilton gi-oup. Scho/iaiie Co., N. Y. 



Nyassa AKGUTA. 



I'ago 354. 



Fig. 7. A cast of the right valve of ordinary form, enlarfjed to show muscular impression and cardinal line. 



Hamilton group. Pitcher springs, Chenaiigo, Co., N. Y. 

 Fig. 8. A giitta-jiei-cha impression from the same. 

 Kgs. 9-11. Three left valves. 

 Rg8. 12, 13. Two right valv<?s of this species. 

 Pig. 14. The cast of the interior of a right valve. 



Hamilton group. Pratt's falU, N. Y. 

 Pig. 15. The cast of the right valve showing musculai- scars, pallial line and hinge i;haractei-8. 



Hamilton group. Pratt's f alii, N. Y. 

 Pig. 16. A gutta-pentha imjiression from the preceding. 

 Fig. 17. A cast of a right valve of an unusually lai-ge individual. 



Hamilton group. Otsego Co., N. Y. 

 Pig. 18. A gutta-i>ei-cha impres,sion from the pi-eceding 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 slbalata. 



PagcSSS, 

 Figs. 21-25. Right and left valves, showing the usual variety of form, the anterior musculai- scar and 

 pallial line. 



Hamilton group. Schoharie Co., N. Y. 

 Fig. 26. A smaller left valve which has ilcveloped distinct I'adii upon the jiosterior slope. 

 Hamilton group. Fultonham, Schoharie Co., N. Y. 



