I'l.ATE I.KXXIX— CoiiUiiued.' 



Ijl.rrOUESMA MOKTONI. 

 Page ISO. 

 Sec Phiti; 21. 

 Fig-. 9. The specimen tig-. 81. plate 21, reiirawn to .show the form of the body and size of the wing-. 



Chemimg f^roui). Porlnllle, Cattaraugus Co., N. Y. 

 Pig. 10. 'I'ho right valve tig. 32, plate 21, redrawn to show the pi-opiir form and charactei-s of this valve. 



Chemung gronp. Portville, N. 7. 

 V\g. II. A cai-dinal view of a specimen, pi'eserving the valves partially njien and .showing their comparative 

 size. Chemung- ^•ouii. TAttle Genesee, N. T. 



I^KITODESMA BiLLINGSI. 

 Page 1!>2. 

 Fig. 12. A large loft valve. 



Chemung group. Panama, iV. Y. 

 Fi"-. 13. A right valve agreeing in form and proportions with this species, l>ut referred with some doubt 

 on account of the geolog-ical po.sition. 



Chemung group. Near Elinira, N. F. 

 Fig. 14. An imperfect left valve of somewhat different form. 



Chemung group. Panama, N. Y. 

 Fig. 1.'). A small left \-alve from the same horizon as the specimen tig. 13. 



liEPTODES-MA LEPIDUM. 



P.lgc 19.i. 



See Plate 21. 

 Fig. 1(5. A li'ft valve showing the form and surface markings. 

 Chemung group. Tinr/n Co. , Pa. 



Leptodesma Aga.ssizi. 



• Page If^-J. 



Figs, n, 18. Two left valves showing the chara<;teristic foi-ni of this species. 

 Fig. 19. A small right valve. 



Clicmung grouji. Ifear Elmira, N. Y. 



Leptodesma Stephani. 



Page 194 

 Fig. 20. A right valve. 



Figs. 21. 22. Two left valves showing the usual characters of the species. 

 Chemnng group. Bradford, Pa. 



LkI'TODESMA DI.SPARILE. 

 Page 180. 

 See Plate 2.5. 

 Fig. 23. A right valve showing the form and ornamentation. 

 Fig. 21 A small left valve preserving the spiniform process. 

 Chemung group. McKean Co., Pa. 



