144 PiiL^ONTOLOGY OF OHIO. 



shell. So far as can be seen from the only imperfect impression exam- 

 ined, it differs somewhat from the original specimens of the species in 

 the more rapid increase of the volutions, and also in the greater number 

 of revolving lines or bands ; and no specimens have been seen that will 

 satisfactorily determine the characters of the umbilical region. It is 

 possible, therefore, that it may yet prove to be an entirely distinct species 

 when better specimens are examined. We, therefore, propose to consider 

 it as a variety of the above species under the varietal name of Ohio- 

 ensis= Trochonema pauper var. OMoensis. 



Formation and locality: In the upper part of the Niagara group (Guelph horizon), 

 Greenville, Ohio. From the Ohio State collection. Collected by Eev. H. Hertzer. 



Genus STRAP AROLLUS, Montfort. 

 Steapaeolltjs Niagarensis (n. sp.). 



Plate 8, flg. 3. 



Shell small, discoidal, consisting of from two to two »nd a half volu- 

 tions in a specimen measuring one inch and three-tenths in its greatest' 

 diameter. Volutions moderately increasing in size, and contiguous to 

 each other, circular in a transverse section, the internal cast showing a 

 space between the filling of two volutions equal to one-sixteenth of an 

 inch, to allow for the thickness of the two walls of shell removed. Spire 

 flat, or having the inner volutions slightly depressed below the plane of 

 the outer one. Umbilical side broad and shallow, but more deeply de- 

 pressed than the spire, exposing almost the entire diameter of the inner 

 volutions, and in the cast showing the entire diameter. 



The surface of the shell, judging from the cast, has been marked by six 

 or more faint, revolving lines or carinse. The two principal and most 

 central ones form a band on the periphery, below which there are three 

 others, and one or two additional ones below. There are also remains of 

 strong, irregular, concentric lines of growth crossing the volutions. 



The species is represented only by internal casts, and in this condition 

 bears a striking resemblance to shells of Euomphalus (Straparollus) laxus 

 and E. (?) noveboracensis, Hall, the volutions having nearly the distance 

 from each other as those of that species which retain the shell ; but if 

 due allowance is made for the thickness of the two shell walls, it will be 

 found that in this species they have been in close contact. In this re- 

 spect it corresponds more nearly with Euomphalus clymenoides, Hall, from 

 the Schoharie grit of New York, from which it differs in the more rapid 



