PLATE LXXIII. 

 MicRODON (Cypricaruklla) oreoabius. 



Pago 309. 

 See Plate 74. 

 Figs. 1-6. Three right and thi-ee left valves showing the principal varieties of form and size. 



MiCRODON (Cypkicardella) BELLISTRIATUS. 



Page 3>;s. 

 See Plates 4:.', 74. 

 Figs. 7-20. A series of specimens illustrating' the principal varieties of form and surface characters. 

 Figs. 21, 22. The left and right sides of a specimen retaining both valves, showing the narrow form of the 

 right valve, as produced by vertical compression. 

 Hamilton grroup. N. Y. 



MiCRODON (CvPRICARDELLA) TENUI8TRIATUS. 



I'ago 310. 

 See Plates 42, 74. 

 Figs. 23, 24. Two right valves. 



Hamilton group. Madison Co., N. Y. 

 Fig. 25. A partial cast of a left valve, showing the anterior muscular scar and surface markings. 



Hamilton group. MctdUon Co., N. Y. 

 Fig. 26. A specimen retaining both valves in conjunction. 



Hamilton group. /Summit, Sclioliarie Co., N. Y. 

 Figs. 27, 28. Right and left valves of elongate form. 



Hamilton group. Shore of Canandaigua lake, N. Y. 

 Fig. 29. A left valve. 



Hamilton group. Madlion Co., N. Y. 

 Fig. 30. The interior of a left valve, as obtained from a gutta-pei-cha impression, showing the hinge area, 

 anterior muscular scar and pallial line. 



Hamilton group. Madison Co., N. Y. 



