PLATE XXXVI. 



MODIOMOKPHA CONCENTUICA. 

 Page -27'). 

 See Plates 34, 35. 

 Figs. 1-12. Showiiij!' the variety of fonn, ni/.e ami surface marking's cliaractei-i.stic of the species. 



Hamilton {fi-oup. Shores of Cayuga, iSeiieca, CaiMiuiaigtm lakes and Pralt's falls, N. Y. 

 Fig. 13. A cai-ilinal view showing' the ligamental ai-ea and ligament. 

 V'lg. 14. A i>ai-tial ca.st of the intei-ior showing the anterior muscular scar and pallial line. 



Hamilton group. Cximbtrland, Md. 

 Fig. 15. The cast of the interior of a left valve showing muscular scars, pallial line, and the striated hinge ^ 



area of the opposite valve.  



Fig. 16. The interior of the left valve, partially obtained by a gutta-percha impression, showing the strong 

 UK>th and the callosity below, with musculai' scar and pallial line. 

 Hamilton gn)up. Cumberland, Md. 

 Fig'. 17. A cast of the left valve showing the anterior muscular scar, the cavity of the tootli and the impnw- 



sion of the striated ligamental aiva. ' 



Fig. 18. A gutta-]iei-<;ha impi-e.ssion from the i)rece<ling, showing moit; clearly the charactei-s of the interim'. 

 Hamilton grwup. Schoharie Co., N. Y. 



MODIOMOKPHA CYMBULA. 



Page 282. 

 Fig. lit. A cast of the interior of a left valve showing the mu.scular .scars and pallial line. 

 Fig. 20. A gutta-pei-cha impression from the pi-cceding. 



Hamilton gi-oup. East Worcester, N. Y. 



MODIOMORPHA AKCUATA. i 



! 

 Page 281. 



Pi(f. 21. A partial ca»t of the interior, preserving' some of the surface markings and showing the anterior 

 muHcular scar. 



Hamilton gi-oup. Schoharie Co., N. Y. 



