PLATE XC— Continued 



Leptodesma Hector. 



Page 209. 

 Figs. 19. 20. The left and right valves of this species The right valve preserves the pallia] line and mus- 

 cular impression. 



Chemung' group. Canton, Bradford Co., Pit. 



Leptodesma Clitus. 



Page '210. 

 Fig. 21. A left valve, showing the form ami surface markings. 

 Chemung group. Mansfield, Pa. 



Leptodesma Corydon. 



Page/ 212 

 Fig-. 22. The left valve described. 



Chemung group. Mansfield, Pa. 



Leptodesma Orcus. 



Page 215. 

 Fig. 23. A left valve. 



Chemung group. Mansfield, Pa. 



Leptodesma truncatlm. 



Page 211 



Figs. 24, 25. A right and left valve of this sjini's. 



Chemung group. Mansfield, Pa. 



Leptodesma alatum. 



Page its. 

 Pig. 26. A left valve. 



Fig. 27. A right valve preserving the pallia] line and muscular impression. The apparent anterior mus- 

 cular scar is due to a defect in the shell, as the pallial line can lie traced to a point just anterior 

 to the beak. 



Chemung group. Canton, Bradford Co., Pa. 



Leptodesma Pelops. 



Page 214. 

 Figs. 2S, 29. Two left valves varying slightly in form and proportions. 

 Chemung group. Mansfield, Pa. 



Leptodesma Orus. 



Page 210. 

 Fig. 30. A left valve showing the form and surface markings. 

 Chemung group. Mansfield, Pa. 



Leptodesma Nereus. 



Page 217. 

 Fig. 31. A mould of an imperfect right valve lying in the left valve, showing the oblique lateral teeth, the 



pallial line and muscular impression. 

 Figs. 32, 33. Two left valves: tig. 33 shows an oblique lateral tooth corresponding to the two in the light 

 valve represented in figure 31. 



Chemung group. Mansfield, Pa. 



Leptodesma Lysander. 



Page 216. 

 See Plate 22. 

 Fit;. 34. A left valve, showing the form ami regular concentric stria 1 of the surface. 

 Chemung group. Mansfield, Pn. 



