Fossils from the Northwest Territory. 165 



Surface of both valves marked by numerous, rather fine, 

 rounded, radiating costce, having an average width of about 

 one miUimeter; costte increasing chiefly by bifurcation; radi- 

 ating markings crossed by finer concentric ridges averaging 

 about half the widlh of the cost«, and by numerous, often 

 sharply pronounced, lines of growth. 



The concentric strice are not equally well developed on all 

 individuals, nor are they always equally well developed on all 

 parts of the same individual. Some individuals are extremely 

 gibbous, others are narrow and elongate. 



An average specimen has a length of two and a half inches, 

 with a width of a little less than two inches, and a thickness 

 of one and three-eighths inches. An elongate, strongl}- arched 

 form has a length of more than three inches and a width 

 about one and three-fourths inches. 



Collected near the Hudson Bay Company's station, Grand 

 Rapids, at the northern end of Lake Winnipeg, b}' Frank 

 Russell and Arthur G. Smith. The geological horizon is 

 Upper Silurian, the strata being probably the equivalent of 

 our Niagara limestone. 



Since the collections made by Messrs. Russell and Smith 

 came to hand, I have received specimens of this species 

 showing slightly different characteristics, obtained from bowl- 

 ders in drift near Virden, Manitoba. 



TWO UNIfiUE SPIRIFERS FROM THE DEVONIAN STRATA OF IOWA. 



By S. CALVIX. 



The two spirifers illustrated on Plate XII of the present 

 Bulletin are already known to geologists. Descriptions of 

 them have for some time been before the public, but hitherto 

 no figures of them have been published. 



