GASTEROPODS. 143 



tened above; very slightly convex below, with a prominent 

 bicarinate peripheral prominence. On the apical portions only 

 the upper of the two carioae is elevated above the sutural line, 

 near which is a thickened, subangular, more or less obscurely 

 nodose ridge. Aperture some what rhombic in shape. Surface 

 marked by a score or more of minute, filiform, revolving lines, 

 of which twelve to fourteen are anterior to the peripheral 

 edge ; these are crossed by small transverse costse. 



Horizon and localities. Upper Carboniferous, Lower Coal 

 Measures : Clinton ( Henry county). 



The specimens examined do not present much variation. 

 The two peripheral carinre are nearly equal, and between them 

 is located the concave band of the sinus. The whorls are 

 ornamented by sixteen or seventeen straight, filiform lines, 

 nine below the lower carina, upon which there are two thread- 

 like elevations ; three above the upper carina, upon which 

 there are two or three lines, and a single line on the sinal band. 

 Crossing the small revolving ridges are numerous well-marked 

 equidistant transverse lines, which give to the whole ornamen- 

 tation a characteristic cancellated appearance. Between, and 

 parallel to, these transverse raised stride are also from three 

 to six microscopic, yet sharp and distinct raised stride. 



Meek and Worthen refer, with a query, to Shumard's 

 species, a form from Macoupin county, Illinois, having about 

 twenty-five revolving lines ( twelve of which occupy the lower 

 side of the body-whorl ), instead of thirteen or fourteen, as 

 ascribed by Shumard to this species. Shumard says : " Sur- 

 face of volutions ornamented with from thirteen to fourteen 

 rather strong filiform stria3, which are crossed by sharp trans- 

 verse stria3." If by this he intends to convey the idea that 

 this is the entire number of lines, including those on the under 

 side of the body-whorl, Meek and Worthen remark that they 

 "should scarcely entertain a doubt in regard to our [ their J 

 shell being a distinct species, since it uniformly has about 

 double that number of revolving stride on the last whorl." 



