22 CONTRIBUTIONS TO CANADIAN PAL^ONTOLOGT. 



North or Second Branch of the Milk Eiver (" nodular layer"), G-. 

 M. Dawson, 1874, H. M. North American Boundary Commission. Old 

 Man Eiver, two miles above Eye-Grass flat, and St. Mary Eiver, 

 three miles north of the 49th Parallel, G. M. Dawson, 1881. All from 

 the St. Mary E. Series. 



As the few Canadian specimens that have yet been collected seem to 

 represent a rather peculiar variety of the species, an original descrip- 

 tion and a figure of one of the best preserved and most perfect speci- 

 mens collected by Dr. Dawson is here given. 



GoNiOBAsis TENUioARiNATA, Meek and Hayden. 

 Plate 3, figs. .5 and 5a. 



Melania tenuicarinata, Meek and Hayden. 1857. Proc. Ac. Nat. Sc. Phil., vol. IX, 



p. 137. 

 Ooniolasis tenuicarinata, Meek. 1876. Eep. U.S. Geol. Surv. Terr., vol. IX., p. 566, 



pi. 43, figs. 14, a, b, o- 



Bow Eiver, two miles below the mouth of Jumping Pound Eiver, Gr. 

 M. Dawson, 1881 ; a few beautifully preserved specimens. 



GoNiOBASis TENUICARINATA, Meek and Hayden, Yar. 



Shell tiirreted, moderatelj^ elongated, the length being rather more 

 than twice the maximum breadth ; sp)ire somewhat longer than the 

 outer volution ; base either imjierforate or possibly with a very narrow 

 fissure in ^jlace of the umbilicus. Volutions seven, the first, second, 

 and third slender but rather ventricose, the three succeeding ones 

 angulated and bearing a distinct narrow and prominent keel a little 

 above the middle, their sides obliquely flattened above the keel and 

 moderately convex or compi-essed in a dii'cction neai'l}- parallel to the 

 axis below it ; suture distinct. Outer whorl angulated and carinated 

 considerably below the centre, strongly convex just below the keel, and 

 narrowing gradually to the base. Aperture broadly subovate, pointed 

 above and narrowly rounded below. 



Sculjiture consisting of numerous and very closely arranged minute 

 revolving lines, which are too small to be visible to the naked eye, in 

 addition to the spiral keel. 



Length, twenty-one millimetres ; maximum breadth, nine milli- 

 metres ; length of outer volution, ten. 



