CAEBONIFBKOUS PERIOD, 161 



Length of the largest specimen in the collection, thirty-six millimeters ; 

 width of the body- volution, twenty-three millimeters. 



This shell varies considerably, especially in the distinctness of the angle 

 and the convexity of the volutions ; but it differs conspicuously from all 

 other known species of Macrocheilus in the possession of such an angle at the 

 posterior part of the whorls as has been described, or, in the absence of it, 

 the somewhat deeply-impressed suture. 



Position and locallti/. — Strata of the Carboniferous period; Camp Cotton- 

 wood, near Spring Mountain, Nevada. 



Class CEPHALOPODA. 



Oeder TETRABRANCHIATA. 

 Family GONIATITID^. 



Genus GONIATITES de Haan, 1825. 



I rom Carboniferous strata upon the east side of Mount Nebo, Utah, 

 a single, very imperfect specimen of Goniatites was obtained." It is too 

 imperfect for specific chai'acterization ; but yet its form and traces of the 

 septa seem to indicate a difference from any known species. The shell is 

 discoid ; sides of the volutions slightly convex, the last one measuring at the 

 aperture half as much as the full diameter across the whorls. 



Family NAUTILID^. 



Genus NAUTILUS Breynius, 1732. 



From strata of the Carboniferous period at the Mesa near Cai'rizo 

 River, Arizona, some fragments of two species of Nautilus were obtained. 

 One is probably identical with N. latus Meek and Worthen, the type- 

 specimens of which were obtained from the Coal-Measures of Illinois. The 

 Oiher is either identical with, or closely allied to, N. Springeri White and 

 Si;. John, the type of which species was obtained from the Upper Coal- 

 Measures of Iowa. 



11 F 



