PI. A IK LXXXLX— Continued.' 



LEPTt tDESMA MORTONI. 



e 190. 

 See Plate 21. 

 Fig-. 9. The specimen fig. 31, plat.. 21, redrawn to show the form of the body and size of the wing. 



Chemung group. I'-rlriil,, Cattaraugus Co., X. J". 

 Pig. 10. The right valve fig. 32, plate 21, redrawn to show the proper form and characters of this valve. 

 Chemung group. Portville, N. Y. 



Pig. 11. A cardinal view of a S] tmen, preserving the valves partially open ami showing- their comparative 



si/e. Chemung group. Little Genesee, N. Y. 



Leptodesma Billingsi. 



Page 19-2. 

 Pig. 12. A large left valve. 



Chemung group. Panama, X. Y. 

 Fig. 13. A right valve agreeing in form and proportions with this species, hut referred with some doubt 

 on account of the geological position. 



Chemung group. Near Elmira, N. Y 

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



Chemung group. Panama, X. Y. 

 Fig. 15. A small left valve from the same horizon as the specimen tig. 13. 



Leptodesma lepidum. 



Page 195. 



See Plate 21. 

 Fig. HI. A left valve showing the form and surface markings. 

 Chemung group. Tioga Co., Pa. 



Leptodesma Agassizi. 

 • Page 183 



Figs. 17. Is. Two h't't valves showing tic characteristic form of this species. 

 Pig. I'.e A small light valve. 



Chemung group. Near Elmira, X. Y. 



Leptodesma Stephani. 



Page 194 

 Fig-. 'Jo. A right vnh e. 



Figs. 21, '-'2. Two left valves showing'- the usual characters of the species. 



Chemung group. Bradford, Pa. 



Leptodesma disparile. 



Page 186. 

 See Plate 25. 

 23. A right valve showing- the form ami ornamentation. 

 Pig. '.'1 A small left valve preserving the spiniform process. 

 Chemung group. McKean Co., Pa. 



