DESCRIPTION OF SPECIES 245 



broadly and slightly sinuous in the middle, and rounding upward at 

 .the extremities; hinge line straight, between one-half and two-thirds 

 as long as the valves, ranging at an angle of about 25 degrees with the 

 oblique, longer axis of the shell, so as to meet the sloping upper edge 

 of the posterior margin at a very obtuse but moderately well-defined 

 angle, thus imparting to the somewhat compressed posterior dorsal 

 region a very faintly alate appearance; beaks extremely oblique, de- 

 pressed nearly to the dorsal margin, very nearly terminal, and scarcely 

 projecting beyond the rounded outline of the anterior extremity. Sur- 

 face ornamented by about fifteen to twenty exceedingly regular, well- 

 defined, subimbricating, flattened, concentric ridges or undulations 

 that gradually become smaller and more closely approximating to 

 the umbones." 



The specimens of this species in the collections examined show no 

 departures from Meek's description. The species has been obtained 

 only from the Lower Mercer and McArthur limestones. 



Dimensions. Length 10 mm., height at beaks 4.2 mm., height 

 near posterior extremity 6 mm. 



Horizon and locality. Widely distributed in the Lower Mercer 

 member of Muskingum and Licking counties, c. McArthur member: 

 Jackson County, Locality 80, c; Vinton County, Locality 84, r. 



Class Scaphopoda 



Genus Plagioglypta Pilsbry and Sharp 

 Plagioglypta meekana (Geinitz) 



1866 Dentaliwn meektanum. Geinitz, Die Carb. und Dyas in Nebr., p. 13, Tab. 1, 

 Fig. 20. 

 Coal Measures: Nebraska City, Nebraska. 



Description. Plagioglypta meekiana is represented in the Lower 

 Mercer limestone by a few scattered specimens. The form is mode- 

 rately curved, is marked by very fine revolving lines which are slightly 

 oblique in position, and ranges in length from about 12 to 22 mm. 



Horizon and locality. Lower Mercer limestone: Muskingum 

 County, Locality 43, r; Stark County, Locality 52, r. 



Plagioglypta prosseri n. sp. 

 PL XVI, figs. 3, 4 



Description. Shell of median size, slightly curved, the greatest 

 curvature occurring in the smaller half of the shell; increasing in size 

 rather gradually toward the large end; form of aperture unknown. 



