Contributions to Invertebrate Palaeontology. 595 



from the Coal Measures, Mercer Co., 111., are almost too slight for 

 specific distinctions, where all the examples are internal casts. In 

 the last-named species the bulk of the volution is on the inner side 

 of the line of nodes in.stead of on the outside as in the one now 

 under consideration, while in the one figured by M. and W. it is 

 very nearly or quite equally divided. Where all other features are 

 the same in all, these would scarcely seem to be of specific import- 

 ance. 



From the strong sinus in the lip on the back of the shell the 

 species has been referred to McCoy's genus Temnocheilus, and 

 would be so classed if that division should be retained. 



Formation and Locality. — In the Maxville limestone (Chester), 

 near Rushville, Ohio, from the collection of Prof. E. B. Andrews. 



IVaiitiliis pauper. 



Plate XIV, fig. 23. ' 



Nautilus pavper Whitf., Ann. N. Y. Acad. Sci., 1882, p. 226. 



Shell somewhat below the medium size, and consisting of about two and a 

 half volutions, which' increase rather rapidly in size, and are so coiled as to 

 expose almost the entire diameter of the inner coils in the umbilical cavity ; 

 the outer one embracing only the dorsal surface of the inner volution. Volu- 

 tions quadrangular in form, with the lateral diameter only about two-thirds 

 as great as the dorso-ventral diameter ; while the dorsal and ventral surfaces 

 are nearly vertical to the plane of the sides, so far as can be determined from 

 the specimen on hand ; or possibly the dorsal surface may be slightly rounded. 

 The sides of the shell are marked by a faint, narrow, revolving sulcus border- 

 ing the margin of the umbilicus, and by a correspondingly faint ridge close to 

 tlie dorsal margin ; while a much stronger rounded ridge occurs on tlie surface 

 at about one-third of the width of the volution from the dorsal border. Inter- 

 nal features of the shell not known. 



A single individual only of the species has been observed, and is 

 altogether too imperfect to reveal all the features. It consists of 

 the non-septate portion of the shell, in the condition of an internal 

 cast, with the impression of one side of the entire shell ; but gives 

 no indications of the septa themselves. The only features indicat- 

 ing its cephalopodous nature, upon which one can rely, are its 

 symmetrical form, and the evidence of a similar ornamentation on 

 the jopposite sides ; otherwase it might have been supposed to repre- 

 sent a form of Euomphalus. 



Formation and Locality. — In the Maxville limestone (Chester), 

 near Rushville, Ohio. Collection of Prof. E. B. Andrews. 



