\ 



NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 99 



eyes the facial suture diverges slightly. Eyes of moderate size, situ- 

 ated rather far forward, so that their anterior ends are about opposite 

 the front of the glabella. They are only slightly bowed, but the palpe- 

 bral lobes lie entirely outside the margin of the fixigene and are set 

 at an angle slightly greater than the course of lateral dorsal furrow. 

 Heavy but low eye ridges are developed. Viewed from the front the 

 cranidium is evenly convex, with glabella and fixigenes forming one 

 curved slope. Longitudinally the convexity is greater but is also even, 

 except for the slight flattening of the brim toward a horizontal posi- 

 tion. The associated libragene has a large occular platform, a raised 

 thickened rim, and a slender genal spine. 



Honey Creek limestone ; (loc. I2p) 4 miles east of Alpers, Arbuckle 

 Mountains, Oklahoma. 



Holotype. — U.S.N.M. No. 108822a; paratypes, Nos. 108822b, c. 



TAENICEPHALUS Ulrich and Resser, 1924 



TAENICEPHALUS PEALEI, new species 



Plate 19, Figures 15-23 



Limestone layers in the Dry Creek formation cropping out from 

 Logan eastward to the Bridger Range, and thence southeastward 

 beyond Livingston, contain a species of Tacnicephalus, often occur- 

 ring in abundance. Most of the rock is a chowder, but here and there 

 cranidia and other parts escaped being broken before entombment. 



This species is characterized by normal features throughout. The 

 glabella tapers at a normal rate. On the outside two pairs of shallow 

 furrows may be traced, but on exfoliated examples three pairs are 

 clearly visible. Where the test remains, the dorsal furrow is rather 

 deep but narrow, and the occipital furrow is prominent both across 

 the glabella and on the large posterolateral limbs. The fixigenes are 

 half the glabellar width at the anterior end of the eyes. Brim width 

 equals half the glabellar length. Preglabellar area rather wide and 

 strongly convex. Rim expanded forward in middle, giving the anterior 

 outline an angulated appearance. Eyes of moderate size and in normal 

 position. 



The pygidium is of normal size and oval shape. The almost com- 

 pletely exfoliated example figured has deeper furrows and greater 

 relief than the exterior would show. The wide axis extends nearly 

 the full length of the tail. 



Although the outside of test seems to be smooth, the preglabellar 

 area and other elevated portions of exfoliated specimens exhibit 



