Contributions to Invertebrate Palaeontology. 525 



inner face. There is no species of similar character from rocks of 

 Devonian age, so far as can be ascertained. On some of the inter- 

 nal casts, there occurs a longitudinal 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 Goleoprion 

 Sandberger, though no positive interruption of the striae of the sur- 

 face is seen on any specimen examined. This fact may suggest its 

 belonging to the recently formed genus Coleolus Hall ; but its per- 

 fect 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 Dentalium, 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 

 Helderberg limestones, near Dublin, Ohio. 



Genus MACUOCHEILUS Phillips. 



Macroclieiltis priscus. 



Plate VII, figs. 3 and 4. 



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



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

 meter 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, equalling 

 fully two-thirds of the entire height. Suture-line distinct, but not strongly 

 marked. Apical angle about eighty degrees. Aperture somewhat semilunate, 

 strongly modified on the inner side by the body of the preceding volution, 

 which occupies fully one-half its height. Columella strong, straight and 

 rounded, and the twisted ridge obsolete. Surface of the shell apparently 

 smooth ; at least no strife are perceptible. 



This pretty little species reminds one strongly of 31. ventricosus 

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

 although resembling it in most other respects. The substance of 

 the shell is soft and chalky, and might not retain minute surface 



