I'l.ATK XC— Coiitiiiuc<l 



Lei'touesma IIkctoh. 



I'lvgC 209. 

 Kijfs. lit. lid. Tlif U'lt anil lifrht valves iif this sppciMs The lig-ht valvi' pi-eserves the imllial line ami mus- 

 cnhir iiiiiiifssion. 



Chi'iniiiifr ffi""!'- Ciinhm, ISriidforil I'n., Pa. 



Leptodesma ("mtus. 



I'agc 210. 

 Kig. 21. A left viilve. .showiiijr the f(irm and .sui-facn markinjr>- 

 Cheniuiiff grroup. Mansfiuld, Pa. 



Lkitooesma Corydon. 



Page -1^. 

 Fij,'. 22. The left valve descnbe<i. 



Chemung grouji. Maiusfielrl , Pa. 



Leptodesma Orcu^. 



Pajre 21.'). 

 Fig. 23. A left valve. 



Chemung gi-diij). Mansfield. Pa. 



Leptodesma truncatlm. 



Page 211. 

 Figs. 24, 2.1. A rig-ht and left valve of this species. 



Chonuing group. Manxfield, Pa. 



Leptodesma ai.aiim. 



Page 21S. 

 Fig. 26. A loft valve. 



P'ig. 27. A light valve pi'eserving the pallial line and nius(-idai- impression. The apparent anterior mus- 

 rulnr scar is due to a defect in the shell, as the pallial line can lie traced to a point jn.st anterior 



to the beak. 



Chemung group. Coiitoii, Bradford Co., Pa. 



TjEptodesma Pelops. 



Page2U. 

 Figs. 28, 21t. Two left valves varying slightly in form and ]>roi>ortious. 

 Chenmng group. MansfirUl, Pa. 



Leptodesma Orus. 



Page 219. 

 Fig. :^0. A left valve showing the foi-m and surfa<:e markings. 

 Chemung group. Mnv.ifi^'UI, Pn. 



Li'.ptodesma Nereus. 



P.ige 217. 

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



pallial line and museidar impression. 

 Figs. 32, 33. Two left valves: tig. 33 shows an oblifpie Lateral tooth corresponding to the two in the right 

 valve rciu-esented in figure 31. 



Chemung grouji. Man.-ifield, Pa. 



Leffodesma Lysander. 



Page 216. 

 See Plate 22. 

 Fig. 34. A left valve, showing the form and regular concentrii' stria- of the surface. 

 Chemung group. MaiiafitM. Pa. 



