yr/r S/)f'f/('S of Fossi/s fi'n/n Ohio. 1'.)!) 



XIII. — Dcscrtj)tionfi of .Neiv Species of Fos.sils from O/iio, icitlt 

 Reniarlcs on mine of the Geological Formaiions in which Ihcij 

 occur. "^ 



V,\ K. p. WUITFIKLJ). 



Head Jauuary lOtli, 1882. 



Species from the Hydraulic Limestones of the Lower Helder- 



berg Group. 



BKACIIIOPODA. 

 Strcptorliynclius liydraulicum, u. sp. 



Pal. Ohio, Vol. Ill, Plate 1, Figs. 1— a. 



Shell small to minute, the largest individuals yet o))Served not exeeediug 

 live-eighths of an incli in greatest diameter, while the most of those ob- 

 served are not more than two-thirds as great. Valves depressed convex, 

 or, more commonly, ai^pearing very flat, as seen on the surface of the stone. 

 Hinge-line straight, neai'ly as long as the width of the shell below, and the 

 latter usually more than the length, frequently nearly' once and a half as 

 great. Ventral valve characterized by a very narrow and nearlj^ vertical 

 cardinal area, and a usually more or less twisted or otherwise distorted 

 beak. Dorsal valve slightly more convex than the ventral, with a percepti- 

 ble mesial depression extending from beak to base, becoming broad and 

 undefined below the middle of the length. Surface of the shell marked by 

 coarse and somewhat ridged radiating strite, which are distinctly alternating 

 in size ; the principal ones proportionally very strong. 



The small size of the shell, Avith the strong radiating and 

 alternate stria?, are distinguishing features of the species. There 

 is no species resembling it, to any degree, among the fossils of 

 New York rocks of a corresponding age. It presents much 

 more the features of forms of the genus from the Coal measures 

 than any heretofore described from Silurian rocks of America, 

 and will not be readily confounded with any known species. 



Formation and Locality. — In the hydraulic beds of the Lower 

 Helderberg group, at Belleville, Sandusky County, and at Green- 



* These descriptions will be reprinted in the forthcoming Volume of the Paleontology of 

 Ohio, and will be accompanied by Illustrations, to which the references by Pla'.e and Figui-e, 

 given in the present article, under each species, relate. 



