NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 85 



end of the eye the fixigene is less than a third the glabellar width. 

 Anterior angles and narrow posterolateral limbs are strongly de- 

 pressed. Surface of exterior granulose, evidently with two sets of 

 granules. Exfoliated surfaces are even more closely covered with 

 coarser granules varying considerably in size. 



Ore Hill formation; (loc. lo'e) i mile south of Ore Hill; and 

 (loc. lojv) ^ mile west of Drab, Pennsylvania. 



Holofypc— v. S.N. M. No. 108842a; paratype, No. 108842b. 



IDDINGSIA Walcott, 1924 

 IDDINGSIA NEVADENSIS, new species 



Plate 16, Figures 15-17 



A cranidium and libragene which were previously identified as 

 /. robusta, differ from that species in several respects. /. nevadensis 

 is characterized by the usual large glabella on which the rear pair of 

 furrows are deep and the next pair short and shallow. A wide occip- 

 ital furrow separates a prominent neck ring. At the anterior end 

 of the eye the fixigenes are about one-third the glabellar width. In 

 width the brim is just half the length of the glabella including the 

 neck ring. It is divided about equally into a somewhat convex pre- 

 glabellar area and a slightly thickened rim. Longitudinally the cranid- 

 ium is convex, the glabella having a nearly even curvature except 

 toward the front, where there is a slight decrease. On the other hand 

 the brim as a w-hole is moderately concave. In cross section the 

 glabella is convex, and the libragenes rise from the dorsal furrow 

 rather steeply. The anterior angles are sharply depressed. Likewise 

 the posterolateral limbs appear to have been considerably depressed. 

 The associated libragene has a large ocular platform and a rim to 

 match the brim width. A heavy genal spine of unknown length is 

 built from the heavy rim and the thickened rear portion of the cheek. 



This species differs from /. robusta in its longer glabella and rela- 

 tively narrower rim. In /. robusta the brim as a whole continues the 

 downward slope of the anterior half of the glabella, thus giving the 

 cranidium much greater convexity. 



Secret Canyon shale; (loc. 61) South of LTamburg Aline, Eureka 

 District, Nevada. 



Holotype. — U.S.N.M. No. 108796a; paratype, No. 108796b. 



IDDINGSIA UTAHENSIS, new species 

 Plate 16, Figures 18-20 



Several cranidia from the Dugway Range are the basis for a species, 

 which in general appearance resembles /. nevadensis. I. utahensis is 



