NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 2^/ 



Brim rather wide, with a thickened, sHghtly upturned rim and a 

 preglabellar area of about equal width. Viewed laterally the pre- 

 glabellar area appears to be merely an extraordinarily wide anterior 

 furrow. That this is not the case is shown in the anterior fixigenes, 

 on which the anterior furrow is clearly seen in normal position. 



Secret Canyon shale ; (loc. 6i) south of the Hamburg Mine, Eureka 

 District, Nevada. 



//o/o/3.'/,r.— U.S.N.M. No. 108668. 



PARAIRVINGELLA INTERMEDIA, new species 

 Plate 4, Figures 25-31 



This is the most common species in the Eureka District. It is char- 

 acterized by great width, comparable to typical Irvingella. The glabella 

 is wide and has a circular outline in front, with the usual furrows 

 clearly defined. It stands completely above the shallow dorsal furrow, 

 and longitudinally attains its convexity in the anterior third. The 

 fixigenes are about half the width of the glabella, contracting in their 

 anterior portions to about half their average width. The long eyes 

 attain their moderate curvature by a sharp bend near their midpoint. 

 The brim is narrow and consists of a thickened upturned rim and a 

 narrow preglabellar area of equal width. The posterolateral limbs 

 are bent down very sharply, while the anterior fixigenes decline into 

 the anterior angles to a lesser degree. 



Secret Canyon shale; (loc. 61) south of Hamburg Mine, Eureka 

 District, Nevada. 



Holotypc and panifypcs.—lJ .S.N M. No. 27018. 



PARAIRVINGELLA HAMBURGENSIS, new species 

 Plate 4, Figures 23, 24 



Development of a wide, vertically striated preglabellar area gives 

 this species somewhat the appearance of Elvinia, but for the present 

 it may remain in Parairvingella. 



The subconical glabella show^s the usual furrows. Although not 

 highly convex in cross section it rises above the fixigenes. Longi- 

 tudinally the rear portion is little curved, but the anterior third curves 

 sharply downward. The brim width is nearly equal to one-fourth the 

 cranidial length and consists of a thickened upturned rim and a pre- 

 glabellar area of about equal width. The fixigenes average less than 

 half the glabellar width and maintain their width except in the anterior 

 portion where there is a reduction of about a third. The test is granu- 

 lated and the preglabellar area marked by vertical lines. 



