PALEONTOLOGY. 481 



NAUTILUS PAUPER. 



Plate X, fig. 23. 



Nautilus pauper 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. Volutions 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' 

 possib y the dorsal surface may be slightly rounded. The sides of the shell are 

 marked by a faint, narrow, revolving sulcus bordering the margin of the umbilicus, 

 and by a correspondingly faint ridge close to the dorsal margin ; while a much 

 stronger rounded ridge occurs on the surface at about one-third of the width of the 

 volution from the dorsal border. Internal 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 indi- 

 cations of the septa themselves. , The only features indicating its cepha- 

 lopodous nature, upon which one can rely, are its symmetrical form, and 

 the evidence of a similar ornamentation on the opposite sides? otherwise 

 it might have been supposed to represent a form of Ewomphajus. 



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

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



31 G. O. 



