PALEONTOLOGY. 481 



NAUTILUS PAUPER. 



PI.ATE 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 Eiwmphalus. 



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

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



81 G O. 



