PLATE XX. 
Leiopteria Conradi. 
Page 159. 
See Plate 8S. 
Fig. 1. A large lef'lrvalve. 
Hamilton group. Canandaigua lake, JY. Y. 
Fig. 2. A specimen of medium size showing strong concentric undulations. 
Hamilton group. Bellona, Yates Co., JY. Y. 
Fig. 4. A left valve. Another figure of this specimen is given on plate 88, fig. 3. 
Leiopteria Bigsbyi. 
Page 165. 
See Plate 88. 
Figs. 3, 11. Two left valves showing the form of the shell and the fine concentric strife. 
Figs. 13, 14. Two right valves. 
Fig. 15. A large left valve. 
Hamilton group. Schoharie Co., JY. Y. 
Leiopteria l^evis. 
Page 158. 
See Plate 17.. 
Fig. 5. A left valve enlarged to two diameters. 
Hamilton g-roup. Ontario Co., N. Y. 
Leiofteria Rafinesquii. 
Page 161. 
See Plates 15 and 88. 
Fig. 6. A small left valve. 
Hamilton group. Skaneateles lake, JY. Y. 
Fig. 7. A larger example showing regular concentric undulations of the surface. 
Hamilton group. Bellona, Yates Co., JY. Y. 
Leiopteria MitcheLli. 
Page 166. 
See Plate 88. 
Fig. 8. A left valve of this species. 
Hamilton group. From a boulder in the town of Cathenne, Schuyler Co., JY. Y. 
Leiopteria Greeni. 
Page 160. 
See Plate 88. 
Fig. 9. A large individual retaining both valves partly opened; showing the left valve and the cardinal 
view of the right valve. 
Hamilton group. Bellona, Yates Co., JY. Y. 
Fig. 12. An imperfect left valve preserving a portion of the test and showing the regular concentric • 
lamellae. 
Hamilton group. From a boulder in the town of Catherine, Schuyler Co., N. Y. 
Leiopteria Oweni. 
Page 170. 
Fig. 10. The specimen described, showing- the right valve and the umbo of the left. 
Hamilton group. Canandaigua lake, N. Y. 
Leiopteria Dekayi. 
Page 164. 
See Plates 19 and 88. 
Figs. 16-18. Three left valves differing somewhat in form and obliquity. 
Hamilton group. Otsego Co., JY. Y. 
Actinopteria DECUSSATA. 
Page 111. 
See Plates 17, 18 and 84. 
Fig. 19. A right valve. The specimen shows the pallialline and muscular impression which features are 
not represented in the figure. 
Hamilton group. Madison Co., If- Y. 
