PALEONTOLOGY. 

 PLATE XIV. 



Page. 



PnioxocYCLfs WYOMiXGENSis Meek 440 



Fiu. 1. View of a Bmall specimen of the species. 



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



Fig. :{. Lateral view of a larger individual, showing the aiTangement of the costse. 



•IIelicoceuas (HKTKKOCEnAS t) siMPLico.si.vTUM Wliitf (See foot-note.) 



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



Helicoceras stevexsoxi ^^^litf 447 



Fig. Cy. L.'iteral view of a large si)ecimen, showing the features of the shell. 



Fig. (1. View of the opposite side of the same sfM'cimen. 



Fig. 7. ISasal view of the same, showing the size of the nmbilicus. 



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

 the secoutl lateral lobe, as far as could bo obtained without endangering the 

 sj)eeinien. Enlarged to two diameters. Obtained from the middle volution of 

 the specimen ligured. 



Heteroceras f xebrascexse M. 4fc II : 451 



Fig. 'J. Diagram of a septnn< from the lower volution of the specimen fignxed. Enlarged 

 to two diameters. Sec also PI. 1.5, Fig. G. 



• The fragment figured is the noA-scptatc portiou of a dextrally-coiled shell of large size, marked 

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

 almut an lighthof 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 lonilit)/.— In ferrugiuous sandstone, East fork of Uever Creek, Black Hills. Fort 

 Benton Oronp. 



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