DESCRIPTION OF SPECIES 207 



viduals, one from the Lower Mercer limestone, and another smaller 

 specimen from the Boggs which is imperfect in lacking the posterior 

 tip. 1 Considerable doubt exists as to the advisability of creating a new 

 species on the basis of the scanty material at hand which is none too 

 well preserved. The holotype from the Lower Mercer member is 

 evidently compressed and probably not entirely uncovered; both speci- 

 mens are in the form of internal casts although a small portion of the 

 shell is retained on the smaller. The form is more closely related to 

 L. arata (Hall) than to any other described species. Comparisons have 

 been made with specimens of the latter species from Missouri with 

 the result that the Ohio species was found to be much larger, probably 

 less convex, more slender, with the posterior portion more extended and 

 the beaks less centrally located. The surface markings are also con- 

 siderably finer. It can be distinguished from L. bellistriata Stevens by 

 its much larger size, more slender produced posterior extremity, and 

 less centrally placed beaks; from L. meekana Mark by its larger size 

 and still more attenuated form. 



Horizon and locality. Boggs limestone: Muskingum County, Lo- 

 cality 26, r. Lower Mercer limestone: Perry County, Locality 35, r; 

 Muskingum County, Locality 45, r. 



Genus Yoldia Muller 



Yoldia glabra Beede and Rogers? 



1899 Yoldia glabra. Beede and Rogers, Kansas Univ. Quart., Vol. -8, No. 3, p. 133, 

 PI. 34, Figs. 4 a, 4 b. 

 Coal Measures: Camerons Bluff, near Lawrence, Kansas. 



Description. A few internal molds as well as several specimens on 

 which the external shell is partially preserved which were obtained 

 from the McArthur limestone have been somewhat doubtfully referred 

 to Yoldia glabra. The size is considerably greater than that of the 

 type specimen, but agrees closely both in size and contour with the 

 form from the Wewoka formation of Oklahoma, which Girty 

 assigned to the same species. 2 The beak of our form, however, is a 

 little higher and more prominent than his figures seem to indicate. 

 The surface sculpture consists of extremely fine, rounded lirae sep- 

 arated by interspaces of about the same width. 



Dimensions. Height 11 mm., width 20 mm., convexity of left 

 valve 3.5 mm. 



the above description was completed a third, more perfect specimen from 

 the railroad cut at Somerset, Perry County, has come to the attention of the writer. 

 The left valve is greatly crushed, while the almost perfect right valve probably 

 shows very nearly the original convexity of the species. The escutcheon is broad 

 and well marked. The dimensions of the specimen are: Length 37 mm., height 

 at beaks 16 mm., thickness of right valve 6 mm. 



2 Girty, G. H., U. S. Geol. Surv., Bull. 544, p. 126, PI. Ill, Figs. 9-15, 1915. 



