428 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



by which it can be distinguished. Indeed, I am much inclined to think 

 there is really no well-defined specific difference, though I have no knowl- 

 edge of the nature of the septa in the forms figured by Favre. D'Orbigny 

 figures a much more compressed shell in the Paleont. Fr., Terr. Crt't, I, pi. 

 129, under Sowerby's name S. constrictus, which, with the exception of its 

 greater compression and smaller size, also nearly resembles some specimens 

 of that under consideration in general appearance. His illustration of a 

 septum of a French specimen, however, will be seen to present rather 

 marked differences from those of all the varieties of the American forms, 

 particularly in the possession of a greater number of the small inner lobes. 



When we take into consideration the variability of these shells, how- 

 ever, as known here, there are certainly some reasons for believing that the 

 whole series might, without impropriety, be included as varieties of S. con- 

 strictus. As Dr. Owen has, however, already separated one of these shells 

 under a new name, I prefer to retain this arrangement until a good series 

 can be compared with the European species. 



Dr. Owen's type should also be compared with S. comj>ressus, of 

 Roemer, which seems to be a similar, but doubtless distinct species, if 

 accurately figured. 



Locality and position. — Dr. Owen's type-specimen came from near 

 Cheyenne River, Dakota, where it was found in the upper part of the Fort 

 Pierre group. Ours is from the same horizon on Yellowstone River, Mon- 

 tana, 150 miles above its mouth. 



Scaphitcs nod os us, var. q u ad r angular is. 



Plate 25, figs. 3, a,b,c; 2, a, o, c ; ami tig. 4. 



Scaphitcs notlosus, var. quadrangular'!*, Meek and Hayden (I860), Proceed. Acad. Nat. Sci. Philad., XII, 



420.— Gabb (1861), Synop. Moll. Cret. Formation, 32. 

 Scaphitcs nodosus, var. exiles, Meek and Hayden (1860), Proceed. Acad. Nat. Sci. Philad., XII, 420. 



This variety differs from the preceding, not only in its usually smaller 

 size, but also in having its periphery flattened, its umbilicus rather larger, 

 and its body-part narrower in its vertical diameter, as well as less straight- 

 ened along its upper margin. Its inner row of nodes will also be seen to be 

 nearer the umbilical margin, and the outer rows near the periphery ; the 

 latter character being of course due to the flattening of the periphery. There 

 will also be seen to be some slight differences in the details of its septa 



