462 University of Kansas Geological Survey. 



Length of a medium-sized specimen, fifty mm. ; greatest 

 breadth, fifteen mm. Pillar arched but apparently without 

 folds. There seems to be no well-marked irregularity in the 

 costse, and parallel ridges or oblong nodes are formed on each 

 whorl . 



This species corresponds more nearly to R. ambigua Stanton 

 than to any other form, and may be a variety of that species. 

 The chief differences are found in the nodes and sutures and 

 an absence of folds in the pillar. The specimens of this species 

 were collected by Professor Williston during the past summer 

 from the Septaria of the Blue Hills shales at Williams' Butte, in 

 Mitchell county. Its discovery is interesting from the fact that 

 it is the first gastropod described from this horizon in Kansas. 

 A poorly preserved specimen belonging to this class, but to a 

 different genus, was found imbedded in the same mass of iron 

 pyrites in which the species B. wiUistonii occurred. 



? Melicoceras corrugatum Stanton. Plate c, fig. 3. 



? Ilelicoceras corrugatum Stanton, 1892, Bull. U. S. Geol. Surv., p. 165, pi. 

 xxxv, fig. 5. 



Original description: "Shell dextral, forming a very low, 

 broad, open spiral ; whorls with an ovate cross-section, increas- 

 ing rapidly in size, apparently not in contact. Surface marked 

 by small, regular, rather closely arranged costfe that pass ob- 

 liquely entirely around the whorl. The costa? are narrrowly 

 rounded, not quite as broad as the interspaces, and without 

 nodes or spines. Full form of the shell and septa not known. 

 The type specimen, which is about half of one volution, meas- 

 ures 105 mm. in length, with sections 10 by 12 mm. at the 

 smaller end, and 18 by 23 mm. at the larger end." 



From Stanton's figure, I am led to believe that a fragment of 

 a shell collected from the Septaria horizon of the Fort Benton 

 belongs to this species. 



