PLATE XC—Continued 
Leptodesma Hector. 
Page 209. 
Figs. 19, 20. The left and right valves of this species The right valve preserves the pallial line and mus¬ 
cular impression. 
Chemung group. Canton, Bradford Co., Pa. 
Leptodesma Clitus. 
Page 210. 
Fig. 21. A left valve, showing the form and surface markings. 
Chemung group. Mansfield, Pa. 
Leptodesma Corydon. 
Pago >212. 
Fig. 22. The left valve described. 
Chemung group. Mansfield, Pa. 
Fig. 23. A left valve. 
Leptodesma Orcus. 
Page 215. 
Chemung group. Mansfield., Pa. 
Leptodesma truncatum. 
• Page 211. 
Figs. 24, 25.,A right and left valve of this species. 
Chemung group. Mansfield, Pa. 
Leptodesma alatum. 
Page 218. 
Fig. 26. A left valve. 
Fig-, 27. A right valve preserving the pallial line and muscular impression.' The apparent anterior mus¬ 
cular scar is due to a defect in the shell, as the pallial line can be traced to a point just anterior 
to the beak. 
Chemung group. Canton, Bradford Co., Pa. 
Leptodesma Pelops. 
Page 214. 
Figs. 28, 29. Two left valves varying slightly in form and proportions. 
Chemung group. Mansfield, Pa. 
Leptodesma Orus. 
Page' 219.' 
Fig. 30. A left valve showing the form and surface markings. 
Chemung group. Mansfield, Pa. 
Leptodesma Nereits. 
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 right 
valve represented .in figure 31. 
Chemung group). Mansfield, Pa. 
Leptodesma Lysander. 
Page 216. 
See Plate 22. 
Fig. 34. A left valve, showing the form and regular concentric strise of the surface. 
Chemung- group). Mansfield, Pa. 
