26 CONTRIBrTIONS TO CANADIAN PALEONTOLOGY. 



sunk a little below that level in others : outer whorl bicarinated or en- 

 circled by two narrow and minute but prominent thread-like spiral 

 keels, one of which is placed on or about the middle of the upper sur- 

 face, and the other around the umbilical margin. Volutions three or 

 three and a half, those of the spire exposed only on the upper or pos- 

 terior surface, the first and earliest part of the second regularly 

 rounded in the middle ; suture distinct and deep. Outer volution 

 flattened above, with a downward inclination, on the inner side of the 

 keel, rounded on its outer side and at the periphery : umbilicus deep, 

 conical and about one-third the entire basal diameter. Aperture 

 rounded in some specimens, somewhat rhomboidal in others, possibly 

 from vertical compression, outer lip thin and simple. 



Surface marked by minute, densely crowded and flexuous, transverse 

 raised strife, in addition to the spiral keels, but the former are too small 

 to be made out without the use of a lens. 



Maximum breadth, five millimetres : height not ascertainable with 

 much accuracy, but evidently much less than the breadth. 



Mouth of the Blind Man Eiver, Township 39, Eange 27, west of 4th 

 Principal Meridian, rather abundant and associated with the preceding 

 species. From the same geological horizon as Limncea tenuicostata. 



It is possible that V. bicincta may jwove only a variety of V. filosa, 

 but at present no intermediate forms have been collected. 



B. FEOM THE LAEAMIE OF THE SOUEIS EIVEE DISTEICT. 



(This is a northern extension of the Fort Union Laramie not at present proved 

 to be stratigraphioally continuous with the "Western Laramie joroper. The speci- 

 mens here descritiecl from the Souris River are from localities in the immediate 

 vicinity of tlie iOth Parallel near the intersection of the 103rd Meridian. See 

 Geol. and Ees. 4'Jtli Parallel, p. 8G el seq., and Report of Progress Geol. Survey 

 Can. 1879-80 p. 16 A.) 



Unio priscus, Meek and Hayden. 



Unio priscus, Jleek and Hayden. 1856. Proc. Ac. Nat. Sc. Phil., vol. VIII., p. 117. 

 " " Meek. 1876. Rep. V. S. Geol. Surv. Terr. vol. IX., p. 516, pi. 43, figs. 



8 a, b, c, d. 



Wood End Depot, Souris Eiver, CI. M. Dawson, 1874, H. M. Xorth 

 American Boundary Commission ; five or six well preserved but very 

 imperfect specimens, in which only the beaks ai d the anterior half of 



