NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 53 



distinguished by their convexity. The associated pygidium is similar 

 to that of B. eumus, differing chiefly in somewhat greater relief of 

 the axis and the portions near the margin, particularly toward the 

 rear. 



Sullivan formation; (loc. 64r) Ranger Brook Canyon, Sawback 

 Range, Alberta. 



Holotype. — U.S.N.M. No. 108723a ; paratypes, Nos. id8>y2^h-d. 



BYNUMIA ARGUTA, new species 

 Plate 9, Figures 13-15 



This species is represented by several examples. Its fairly wide 

 glabella is square in front and rounded at the anterior angles. As a 

 whole the outline is nearly that of an equilateral triangle. A shallow 

 dorsal furrow, visible on the exterior, separates the brim from the 

 glabella. The brim is considerably swollen in front. From the front 

 the cranidial cross section is little curved, except at the outer edges. 

 Since the posterolateral Hnibs are greatly depressed in the rear, the 

 cranidium is highly arched. Longitudinally the curvature is moderate, 

 except at the very front, where the swollen rim drops steeply. The 

 associated pygidium is flat and so fused that the axis is scarcely 

 traceable. 



Sullivan formation; (loc. 66s) Badger Pass, Sawback Range, 

 Alberta. 



Holotype. — U.S.N.M. No. 108724a ; paratype. No. To8724b. 



BYNUMIA WALCOTTI, new species 



Plate 9, Figures 16-20 



Bynuinia eumus Walcott (part), Smithsonian Misc. Coll., vol. 75, No. 3, 

 pi. 17, figs. 5, 6, 1925. 



This species was included by Walcott in B. eumus. which it re- 

 sembles. It is abundantly represented at several localities by many 

 specimens. Compared with B. eumus, B. zvaleotti appears to be a 

 stockier form, particularly when not exfoliated. This appearance is 

 due to the more convex and slightly narrower brim. The pygidium 

 assigned to the species is flat, with the poorly defined axis raised 

 slightly above the flat pleural lobes. 



Sullivan formation; (loc. 66m) 5 miles northwest of Banff, and 

 (loc. 66s) Badger Pass, Sawback Range, Alberta. 



Holotype. — U.S.N.M. No. 108731a; paratypes, Nos. 70256, 

 108731b. 



