NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 7I 



At the eyes the fixigenes are half the width of the glabella. The width 

 of the simple, gently concave brim is a little less than the glabellar 

 length. The eyes are slightly larger than usual. In both directions 

 the convexity of the cranidium amounts to little. 



The pygidium from a nearby locality, assigned to the species, has 

 a prominent axis which tapers somewhat more than usual. The rear 

 border occupies about one-third the pygidial length, which with the 

 rather large eye, indicates the approach to Coosio. 



Sullivan formation; (Iocs. 64i, 64c) Glacier Lake Canyon Valley, 

 48 miles northwest of Lake Louise, Alberta. 



Holotype. — U.S.N.M. No. 108762; paratype. No. 108770. 



MARYVILLIA MONTIS, new species 

 Plate 13, Figures 11-13 



Several cranidia and pygidia are in hand. The glabella which tapers 

 to a rounded front, is almost without trace of furrows but does have 

 a faint keel. In this species the brim is rather wide, equaling one- 

 third the cranidial length. A slightly thickened rim, separated by a 

 wide anterior furrow, can be seen when the specimen is lighted from 

 the front, but when the direction of lighting is changed the brim 

 appears to be concave without a rim. At the eye the fixigenes are 

 about half the glabellar width. Longitudinally the cranidium is nearly 

 flat. However, the glabella is gently convex and the preglabellar area 

 depressed, while the brim rises until its anterior half extends above 

 the level of the glabella. In cross section there is little convexity. 



The prominent pygidial axis occupies three-fourths the length of 

 the pygidium and has a postaxial ridge that reaches practically to the 

 rear margin. Axial and pleural furrows shallow. Moderate convexity 

 is developed in both directions. 



Deadwood formation; (loc. 17L) ^ mile west of Deadwood, Black 

 Hills, South Dakota. 



Holotype. — LI.S.N.M. No. 108763a; paratype. No. 108763b. 



MARYVILLIA HYBRIDA, new species 



Plate 13, Figures 14-17 



Although this species is not fully typical of the genus, the cranidial 

 and pygidial characters appear to be closer to Maryvillia than to any 

 other described genus. Therefore M. hybrida is placed in this genus 

 for the present. The exfoliated cranidium has a glabella that tapers 

 to a rounded front. The occipital ring is narrow. No trace of glabellar 

 furrows remains. The brim width equals nearly one-third the 



