CRETACEOUS FOSSILS. 441 



Surface of the shell marked by transverse ridges, which are extremely 

 variable in strength and in the manner of their grouping- on different indi- 

 viduals and at different stages of growth, there being generally a stronger 

 ridge developing nodes at each extremity, with from two to five smaller 

 ones between. The inner nodes are often formed by the coalescing of 

 two or three of the ridges, though sometimes single ; the outer nodes are 

 obliquely longitudinal and flattened on the back, formed by the thickening 

 of the principal rib or by the union of two or more. On the dorsum the 

 ribs continue, but are much subdued and subequal, and directed strongly 

 forward, forming cren illations in crossing the keel. 



Septa rather simple and closety arranged ; the lobes and saddles of the 

 adjacent ones passing within each other, as shown on small individuals. 

 Those of larger individuals not observed. 



This species was first indicated by Mr. F. B Meek in Dr. Hayden's 

 report of 1 870, as Ammonites serrato-carinatus ; but, on learning that this name 

 had been previously used for a similar species, he subsequently proposed 

 the specific name Wyoming 'ensis to be used, providing the two should be 

 found to belong to the same section ; and as we found it so labeled in the 

 collection at the Smithsonian Institution, we infer that he intended to adopt 

 the name, and we have therefore so used it. 



Formation and locality. — In silico-calcareous layers of Division No. 2, 

 Cretaceous, on the east fork of Beaver Creek, near Camp Jenney, Black 

 Hills. 



SCAPHITID^E. 



Genu? SCAPHITES Parkinson. 



SCAPHITES NODOSUS. 



Plate 13, fig. 12. 



Scaphites nodosus Owen, Kept. Geol. Surv. Iowa, Wis. and Minn., 1852, p. 580, tab. 8, 



fig. 4. 

 Scaphites nodosus (Owen) M. & H., Proc. Acad. Nat. Sci. Phil., vol. 12, p. 420. 

 Scaphites nodosus (Owen) Gabb., Synop. Moll. Oret. Formation, p. 32. 

 Scaphites nodosus (Owen) Meek, Smithsonian Check List Cret. Foss., p. 24. 



The examples of this species in the collection are so exactly similar to 

 the figure given by Dr. Owen (Report on the Geological Survey of Iowa, 



