424 GEOLOGY OF OHIO. 



is no species of similar character from rocks of Devonian age, so far as 

 can be ascertained. On some of the internal casts, there occurs a longi- 

 tudinal ridge, as if there had been a slit or interruption of some kind at 

 that point, which gives rise to a supposition that it may have belonged to 

 the genus Coleoprion Sandberger, though no positive interruption of the 

 striae of the surface is seeu on any specimen examined. This fact may 

 suggest its belonging to the recently formed genus Coleolus Hall; but its 

 perfect resemblance to Dentalium more strongly indicates its affinities as 

 in that relation, rather than with the Pteropoda. Nor does there appear 

 any sufficient reason among the species referred to Coleolus by its author, 

 for a generic separation from Dentalhun, other than their more strictly 

 straight form. But there are straight or nearly straight Dentalia, and 

 also curved forms which he has referred to the new genus. The generic 

 feature "shells thick" would also be opposed to pteropodous affinities. 

 In its more rapid taper and greater curvature, it is sufficiently distinct 

 from described forms of that genus. 



Formation and Locality. — In the cherty layers of the Upper Helder- 

 berg limestones, near Dublin, Ohio. 



Genus MACROCHEILUS Phillips. 

 Macrocheilus priscus. 



PLATE III, figs. 3 and 4. 

 Machrocheilus priscus Whitf., Ann. N. Y. Acad. Sci., March, 1882, p. 204. 



Shell small and very ventricose, the height but little greater than the diameter 

 of the body volution ; the former in the figured example being three-eighths of an 

 inch, and the latter only about one-sixteenth of an inch less. Shell composed of 

 about four volutions, which are very ventricose and rapidly increase in diameter, 

 the last one forming the great bulk of the shell, equaling fully two-thirds of the 

 entire height. Suture line distinct, but not strongly marked. Apical angle about 

 eighty degrees. Aperture somewhat semilunate, strongly modified oa the inner 

 side by the body of the preceding volution, which occupies fully one-half its 

 height. Columella strung, straight and rounded, and the twisted ridge obsolete. 

 Surface of the shell apparently smooth ; at least no striae are perceptible. 



This pretty little species reminds one strongly of M. ventricosus 

 Hall, from the Coal-measures, but is somewhat shorter in the spire, al- 

 though resembling it in most other respects. The substance of the 

 shell is soft and chalky^, and might not retain minute surface striae if 

 they had ever existed; but no remains of them are visible at present. 



Formation and Locality. — In the white chert3 r layers of the Upper 

 Helderberg group, near Dublin, Ohio. 



Genus LOXONEMA Phillips. 



Loxone??ia parvidum. 

 Plate III, fig. 5. 

 Loxonema parvulum Whitf., Ann. N. Y. Acad. Sci., March, 1882, p. 204. 



Shell minute, scarcely exceeding a fourth of an inch in length, and propor- 

 tionally slender, with a rapidly ascending spire, which is slightly more rapidl}* 



