PALEONTOLOG-Y. 

 PLATE XIV. 



Page. 

 Prionocyclus wyomingensis Meek 440 



Fig. 1. View of a small specimen of the species. 



Fig. 2. Back view of the same, showing the carina and continuation of the ridges. 



Fig. 3. Lateral view of a larger individual, showing the arrangement of the costs. 



* Helicocekas (Heteeoceras ?) simplicostatum Whitf (See foot-note.) 



Fig. 4. View of the fragment, showing the features described. 



HELICOCERAS STEVENSOiN'I Whitf 447 



Fig. 5. Lateral view of a large specimen, showing the features of the shell. 



Fig. 6. View of the opposite side of the same specimen. 



Fig. 7. Basal view of the same, showing the size of the umhilicus. 



Fig. 8. Diagram of the dorsal and first lateral lobes of a septum, together with a part of 

 the second lateral lobe, as far as could be obtained without endangering the 

 specimen. Enlarged to two diameters. Obtained from the middle volution of 

 the specimen figured. 



HETEROCERAS ? NEBRASCENSE M. & H 451 



Fig. 9. Diagram of a septum from the lower volution of the specimen figured. Enlarged 

 to two diameters. See also PL 15, Fig. 6. 



* The fragment figured is the non-septate portion of a dextrally-coiled shell of large size, marked 

 by simple, angular, revolving costa?, which are nearly vertical on the dorsal side of the shell, and distant 

 about an eighth of an inch between crests. Intercostal spaces concave. At somewhat regular distances, 

 of about one-fourth of the revolution, there is a distinctly stronger costa, which is irregularly nodose 

 on the dorsum. Septa unknown. It is a distinct and strongly marked species. 



Formation and locality. — Iu ferruginous sandstone, East fork of Bever Creek, Black Hills. Fort 

 Benton Group. 



