DESCRIPTION OF SPECIES 213 



referred to the same species with some doubt. The individuals are con- 

 siderably distorted and apparently resemble P. longa more closely than 

 Herrick's species. The posterior outline below the hinge line is more 

 sinuous and the posterior portion of the body more produced than in 

 P. ohioense, yet on a stratigraphic basis identification with the latter 

 species is much more plausible than with P. longa. The imperfect 

 condition of the material renders any specific identification uncertain. 

 Horizon and locality. Lower Mercer limestone: Scioto County, 

 Locality 31, r; Perry County, Locality 35, r; Muskingum County, 

 Localities 43 (c), 45 (r); Licking County, Localities 46 (r), Flint Ridge, 

 47 (c), 48 (r). Me Arthur limestone: Jackson County, Locality 80, c. 

 Black Flint: Jackson County, Locality 87, r; Vinton County, Locality 

 91, r. 



Genus Pseudomonotis Beyrich 

 Pseudomonotis sp. 



Description. Fossils belonging to the genus Pseudomonotis occur 

 in the Lower Mercer limestone but are too poorly preserved to be de- 

 termined specifically. They are small in size and although the com- 

 plete outline cannot be observed, they show a surface sculpture of 

 flexuous costae with vaulted scale-like projections which alternate with 

 smaller costae; still smaller radiating lines cover the interspaces. Her- 

 rick cites as cf. Pseudomonotis radialis an apparently closely related 

 form from the Lower Mercer limestone on Flint Ridge which resembles 

 the form under discussion in Surface sculpture although exact com- 

 parisons of the contour are impossible. 1 



Horizon and locality. Lower Mercer limestone: Perry County, 

 Locality 35, r; Muskingum County, Locality 43, r. 



Genus Posidonia Bronn 

 Posidonia ? acosta (Cox) ? 



1857 Avicula acosta. Cox, Geol. Rep. Ky., Vol. 3, p. 572, PL 9, Fig. 3. 



Coal Measures: Union County, Kentucky; Gallatin County, Illinois. 



Description. A single valve of a small pelecypod with the outline 

 of Placunopsis recticardinalis was obtained from the Lower Mercer 

 limestone of Coshocton County. However, all traces of the radial 

 sculpture, characteristic of the genus Placunopsis, as well as the usual 

 superimposed markings, are entirely wanting. But the absence of the 

 peculiar superimposed markings is perhaps of little importance on a 

 single specimen as the shell may have been attached to a smooth or 

 derrick, C. L., Bull. Den. Univ., Vol. 2, p. 145, PL 14, Fig. 26, 1887. 



