DESCRIPTION OF SPECIES 205 



large size for the Pottsville formation of this State, obtained from the 

 Lower Mercer member in Baltimore & Ohio Railroad cut at Somer- 

 set, has the following measurements: length 33.5 mm., height at beaks 

 18 mm. 



Horizon and locality. Lowellville limestone: Muskingum County, 

 Locality 19, r. Boggs limestone: Muskingum County, Locality 26, r. 

 Widely distributed throughout the Lower Mercer limestone, c 

 McArthur limestone: Jackson County, Locality 80, c; Vinton County, 

 Locality 84, c. 



Leda inflata Girty mss. 

 PI. X, figs. 22-24 



Description. Girty's manuscript description is quoted below: 

 "Shell small, rarely exceeding 8 mm. in width, transversely subovate. 

 Basal margin gently convex, slightly sinuate behind, more rapidly 

 curving in front. Anterior extremity rather regularly rounded below the 

 prominent and backwardly turned beaks. Behind the beaks the out- 

 line is concave, strongly contracting with the base to form a pointed 

 posterior extremity. Beaks slightly anterior to median line. Convexity 

 high, declining rapidly behind the beaks where a sort of constriction 

 occurs which produces more or less of a sinus in the basal outline and 

 gives the posterior extremities a compressed appearance in contrast 

 with the subglobose shape of the major part of the shell. Umbonal 

 ridge high, forming the posterior-superior outline, the post-umbonal 

 slopes being directed almost horizontally, though projecting somewhat 

 at their juncture. 



" Surf ace finely and evenly striated. 



"It cannot be said that we know precisely what form the name 

 Leda bellistriata was intended to cover, but from the shells commonly 

 passing as that species L. inflata differs in its smaller size, its more rap- 

 idly tapering shape, and its more inflated anterior portion." 



Remarks. A small species of Leda from the Sharon ore of Ohio is 

 in all probability the same form as that described above by Girty from 

 the Morrow formation of Arkansas. Its association in this State with 

 N. subrotundata and N. lunulaia, with which it is also associated in the 

 Morrow formation, helps to strengthen this conclusion. L. inflata is 

 characterized by its small size, its short depressed posterior end, and 

 its inflated anterior end. The Ohio form differs in having a slightly 

 less rapidly tapering posterior end, with less contrast between the com- 

 pressed posterior and the inflated anterior ends. These differences, 

 however, may be due to the fact that the Sharon specimens occur as 

 internal casts, while the shell is preserved on the Morrow forms. 



Horizon and locality. Sharon ore: Lick Run, Scioto County, 

 Locality 2, c. 



