PLATE LXXIV. 
MlCRODON (Cl TRICAR DELLA) GREGARIUS. 
Page 309, 
See Plate 73, 
Figs. 1, 2. Right and left valves. 
Chemung group. Cortland, N. Y. 
Fig. 3. A left valve of more elongate form. 
Fig. 4. A small left valve enlarged to two diameters. The strise are represented as too regular and the 
beak too elevated. 
Chemung grouji. Near Elmira, N. Y. 
Microdon (Cypricardella) bellistriatus. 
Page 308. 
See Plates 42, 73. 
Figs. 5, 6. Two right valves of elongate form. 
Chemung group. Near Elmira, N Y. 
Figs. 7, 8. Right and left valves. 
Lower Chemung group. Ithaca, N. Y. 
Fig. 9. The hinge of a left valve showing cardinal teeth and ligamental area, enlarged. 
Hamilton group. Shore of Skaneateles lake, N. Y. 
Fig. 10. The hinge of a light valve, showing- similar characters, enlarged. 
Microdon (Cypricardella) reseryatus. 
Page 312. 
Figs. 11-13. Three valves showing the principal characters of this species. 
Waverly g-roup. Licking Co., Ohio. 
Microdon (Cypricardella) complanatus. 
Page 311. 
See Plate 42. 
Figs. 14-18. A series of valves showing the principal variations in size and form of this species. 
Hamilton group. Schoharie Co., N. Y. 
Fig. 19. The interior of a right valve, as obtained from a gutta-percha impression in a natural mould, 
showing hinge characters, anterior muscular scars and pallial line. 
Microdon (Cypricardella) tenuistriatus. 
Page 310. 
See Plates 42, 73. 
Figs. 21, 22. The hinges of a left and a rig-ht valve showing cardinal teeth and ligamental area, enlarged to 
two diameters. 
