580 UNITED STATES GEOLOGICAL SURVEY OE THE TERRITORIES. 



flattened whorls, and the absence of distinct revolving ridges on the middle 

 of its volutions. It also never has the distinct revolving lines generally seen 

 on that shell. Like several of our other Upper Missouri fresh-water shells, 

 it has some living analogues among Asiatic species, of which P. Francisci 

 (— Turbo Francisci, Wood) is an example. 



From the fresh- and brackish-water beds at Bear River City on the 

 Union Pacific Railroad, in "Wyoming, I have seen a single imperfect speci- 

 men of the middle and upper volutions of a Viviparus that I am much 

 inclined to believe belongs to this species. So far as can be seen, it presents 

 no reliable differences ; but possibly perfect specimens might show it to be 

 distinct. 



Locality and position. — Mouth of Judith River, Montana ; from the 

 Judith River brackish-water beds : probably belonging to the closing period 

 of the Cretaceous. 



Viviparus pec u Maris, M. & H. 



Paludina peculiaris,Mepk and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 122. 



Fl s- 79 - Of this form I have only seen very imperfect speci- 



mens; but so far as can be determined from those yet 

 found, about the only differences that can be seen between 

 it and the last consist in the rather decidedly less flattened 

 nviparus peculiar. form of itg uppe| . volutionSj which also indicate a rather 



greater proportional breadth for the upper part of the shell. I am much 

 inclined to think it only a variety of that species ; but as it comes apparently 

 from a different horizon, I have concluded to keep it separate until we can 

 have better materials for comparison. 



The foregoing cut represents the best specimen seen, with the upper 

 volutions restored in dotted lines. None of the specimens show the aperture 

 very satisfactorily. 



Locality and position. — Fort Clarke, Dakota ; from the Fort Union 

 Lignite group (probably Eocene). 



Viviparus trochiformis, M. & H. 



Plate 44, fig. 2, a, h, c, d, e. 



Pahidina trochiformis, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 122. 



Viripara trochiformis, Meek and Huydeu (I860), ib., XII, 185. 



Viviparus trochiformis, Meek and Hayden (1863), in Professor Gill's paper on the Viviparidos, 6. 



Shell conoid-subtrochiform, rather thin; spire moderately elevated, 

 pointed at the apex ; volutions six, obliquely compressed, though not quite 



