PLATE XC. 



b — Umbonata. 

 Leptodesma Medon. 



Page 197- 

 Figs. 1-3. Three left valves varying somewhat in form and size. 

 Fig. 4. A. right valve of this species. 



Chemung group. Lawreiiceville. Tioga Co.. Pn 



Leptodesma Mentor. 



Page 205. 

 See Plate 23. 

 Fig. 5. A left valve of the usual form. 



Chemung group. Smeiliport, Pa. 



Leptodesma Cadmus. 



Page 201. 

 Fig. 6. A left valve of a specimen preserving both valves partly open. 

 Chemung group. Smithfield, Bradford Co., Pa. 



Fig. 7. A large left valve. 



Chemung group. Steuben Co.. N. T. 



Leptodesma Oeodes. 



Page 206. 

 See Plate 25. 

 Fig. 8. The specimen fig. 9, plate 25, redrawn to sh< w the true form of the body and wing 

 Chemung group. Smethport. Pa. 



Leptodesma ombonatum. 



Pago 1 - 

 See Plate 22. 

 Fitr. 9. The specimen tig. 13. plate 22, redrawn to show its proper form and proportions, 

 Chemung group. Twenty Mile creek, Chautauqua Co., N. Y. 



Leptodesma umbonatom, var. depressum. 



e 199. 

 See Plate 22. 

 Fig. 10. The specimen tig. 14, plate 22. redrawn and restored in outline. 



Chemung group. Napoli Centre, Cattaraugus Co., N. Y 



Leptodesma Creon. 



Page 202 



Figs. 11, 12. Two left valves showing slight differences in form and surface markings. 



Pig. 13. A right valve. 



Chemung group. I , Tioga Co., Pa. 



Leptodesma Loxias. 



Page 204. 

 Fig. 14. A left valve of this species. 



Chemung group. /< Co., Pa. 



Leptodesma Demtjs. 



Page 203. 

 Figs. 15, 16. A right and left valve showing the usual form of the shell. 

 Chemung group. Lawn Vioga Co., Pa. 



c — Rostrata. 

 Leptodesma extenuatdm. 



Page 207. 

 Plato 22. 

 Fig. 17. The specimen fig. 23. plate 22. redrawn to show- the entire form and proportions. 

 Fig. IS. A right valve with the test removed showing the pallial line and muscular impr 

 Chemung group. Mansfield, Tioga Co . Pa. 



