LNVEHTEBKATE PALAEONTOLOGY. 437 



[Soriimi /-. of subgenus Discoscaphites.] 



Scaphites Cheyenne n sis, Owen (sp. ). 



Plate 35, tigs. 3, a-i. 



Ammonites Cheyeitnt iisi8yOwen( 1852), U.S. Geol. Report Wisconsin, Iowa, and Minnesota, 578, pi. vii, fig. 2. 



Ammonites Kebrascensisl, Owen (1852), it., pi. viii. fig. •,'. 



Ammonites Moreauensis, Owen (1852), ib., 5?!*, pi. viii, tig. ?. 



Scaphites Conradi (pait), Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., viii, 281. 



Scaphites Cheyennensis, Meek and Hayden ( I860 i. il> . xii, 420. 



Shell slightly oval or subcircular, compressed ; umbilicus very wide, 

 shallow, and showing about half the breadth of each inner whorl ; volutions 

 increasing gradually in size, a little compressed laterally ; last one but slightly 

 deflected from the regular curve of the others, rather narrowly flattened on 

 the periphery, and subrectangular, but not dilated or straightened along the 

 umbilical side, scarcely or not at all free at the aperture, which has a sub- 

 cordate outline; surface ornamented by distinct, rather angular, slightly 

 flexuous costa?, which increase in number chiefly by the intercalation of two, 

 three, or more shorter ones, between each two of those that pass entirely 

 across from the periphery to the umbilical side, all passing straight over the 

 periphery, and, excepting on the last half of the outer volution, bearing on 

 each side small nodes so arranged as to form four or five revolving rows, 

 exclusive of a row of larger ones on each side of the flattened periphery. 



The septa of this species are divided into lobes and sinuses so nearly 

 like those of S. Conradi, already described, that they can be sufficiently 

 characterized by pointing out the i'ew differences. In the first place, it may 

 be mentioned that both its lobes and sinuses are all proportionally a little 

 wider and shorter than those of *S. Conradi, while its siphonal lobe has its 

 terminal divisions a little more spreading, and only one instead of two slender 

 dentate lateral branches. Its first lateral sinus is less deeply divided by its 

 auxiliary lobe, while its two terminal divisions are of more nearly equal size, 

 the left division being also distinctly tripartite. Its first lateral lobe has a 

 proportionally broader body, and its two terminal divisions are more spreading 

 and more equally bipartite. The difference of its second lateral sinus from 

 1 hat of <S. Conradi, are of a similar nature to those seen in its first ; and the 

 same may be said in regard to its second lateral lobe. Its third. lateral lobe 

 is, like the other, shorter and wider than that of S. Conradi, and more ecpially 

 bipartite, with much shorter divisions; while its fourth lateral lobe differs 

 very little, excepting in breadth, from the corresponding lobe of S. Conradi. 



