PLATE XC. 



b — Umbonata. 

 Leptodesma Medon. 



Page l'J7. 

 Figs. l-;i. Three left valves varying- somewhat in form and size. 

 Fiy. 4. A right valve of this species. 



Chemung group. Lawreiiceville. Tioga Co.. Pa. 



Leptodesma Mentor. 



Paste '20.5. 

 See Plate 23. 

 Fig. 5. A left vah'e of the usual form. 



Chemung group. Smethport, Pa. 



Leptodesma Cadmus. 



Page 'JOl. 

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

 Chemung group. Smithfield, Bradford Co., Pa. 



Fig. 7. A large left valve. 



Chemung group. jStcnheii Ca., N. Y. 



Leptodesma Orodes. 



Page 206. 

 See Plate 25. 

 Fig. 8. The specimen fig. 9, plate 25, redrawn to slinw the true form of the liudy ami wing. 

 Chemung group. Smethport. Pa. 



Leptodesma umbonatum. 



Page 19S. 

 See Plate 22. 

 Fig. 9. The specimen tig. 13, plate 22, redrawn to show its proper form nnd projiortions.. 

 Chemung grouii. Tiiv.nly Mile creek. Clmutauqua Co.. N'. Y. 



Leptodesma umbonatdm, var. deprkssum. 



Page 199. 

 See Pl.ate 22. 

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



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



Leptodesma Creon. 



Page 'la-i. 

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



Fig. 13. A right valve. 



Chemung group. Lawreiu-eriUe, Tioga Co., Pa. 



Leptodesma Loxias. 



P.age '204. 

 Fig. 14. A left valve of this species. 



Chemung gronp. LawreneevUle, Tioga Co.. Pa. 



Leptodesma Demus. 



Page 203. 

 Figs. 15, 1(5. A right and left vah'e showing the usual form of the shell. 

 Chemung group. Lawrencevillr. Tioga Co., Pa. 



c — Rostrata. 

 Leptodesma extenuatum. 



Page 207. 

 See Plate 22. 

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

 Fig. 18. A right valve with the test removed sho\ving the pallial line and muscidar impression. 

 Chemung group. MansfieUl, Tioga Co., Pa. 



