246 POTTSVILLE FAUNA OF OHIO 



Surface ornamented by very fine, closely arranged lines of growth, 

 passing a little obliquely around the shell, with a faint, barely notice- 

 able revolving groove occurring at more or less regular intervals, about 

 3 to 3.5 mm. apart near the larger end but gradually becoming closer 

 together near -the smaller extremity. 



Dimensions. Length of a cotype which probably represents al- 

 most a complete individual 78 mm., diameter of the much flattened 

 larger end 11.5 mm.; diameter near the small end which is also flat- 

 tened 2.5 mm. 



Remarks. Plagioglypta prosseri is of rare occurrence and has been 

 found at only a few localities in the Lower Mercer and Me Arthur lime- 

 stones. The specimens studied include many imperfect specimens as 

 well as two almost complete individuals, an external mold and an 

 internal cast. 1 Both are crushed so that the true diameter and the 

 shape of the aperture cannot be determined. The species is char- 

 acterized by its median size, its slightly curved form, and its fine ob- 

 lique surface markings. It resembles P. canna (White) very closely, 

 but the latter species can be distinguished by its straighter, still more 

 tapering form, and larger size. The fact that P. canna occurs in a 

 much higher portion of the Coal Measures from a far distant locality 

 (common in the Permian of Arizona and New Mexico) lends additional 

 weight to the differences cited above. From P. meekiana (Geinitz) it 

 differs principally in its less curved form and much larger size, the 

 length of the latter species according to Professor Geinitz' measure- 

 ments being .60 to .70 inch. 



Horizon and locality. Lower Mercer limestone: Perry County, 

 Somerset, Locality 35, r; Muskingum County, near Fairview School, 

 Locality 45, r; Licking County, Bald Knob, Locality 46, r. Me Arthur 

 limestone: Jackson County, Monroe Furnace, Locality 80, r; Vinton 

 County, Moore mine near McArthur, Locality 84, r. The specific 

 name is given in honor of Dr. Charles S. Prosser. 



Class Gastropoda 

 Minute Gastropoda (Three or more species) 



Description. Extremely minute gastropods are abundant in the 

 Sand Block ore, but they occur in a much decomposed, macerated 

 condition. Three species were distinguished although more are prob- 

 ably present; all are internal casts showing none of the surface mark- 

 ings. One species has a spire of median height with three or four 

 rapidly enlarging volutions; the body whorl is large and greatly expanded, 



x The internal cast belongs to the collections of Dr. George H. Girty, by whom 

 it was loaned for the purpose of studying the internal characters which are not shown 

 on the writer's specimen. 



