NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 4I 



by a change in slope. The pygidium is flatly convex in transverse 

 section, but as may be observed from the illustration is much steeper 

 in the opposite direction. The species is of average size and the 

 surface seems to have been smooth. 



Signal Mountain formation; (loc. i86s) 4 miles northwest of 

 Ravia ; (loc. 201 j) Royer Ranch, Honey Creek, Arbuckle ^vlountains, 

 Oklahoma. 



Holotype. — U.S.N.M. No. 108693; paratypes, Nos. 108694a, b. 



PLATYCOLPUS WICHITAENSIS, new species 

 Plate 6, Figures 26-29 



This species is represented by several cranidia and a pygidium, and 

 even by a fragment of a libragene. P. zvichitacnsis averages slightly 

 smaller than P. oklalwiiirnsis. The fragmentary cranidium figured 

 has a faint dorsal furrow behind the eyes, and in both lateral and 

 longitudinal sections is evenly and considerably arched. The eyes are 

 of normal size and are situated about the midpoint of the cranidium. 

 The brim is sharply demarcated, thickened, and heavily striated. 



The pygidium on the same piece of rock with a cranidium of 

 Eurekia, is also highly arched in both directions and shows faint 

 dorsal and axial furrows. 



Signal Mountain formation ; (loc. I2g) 2 miles southwest of Signal 

 Mountain, Wichita Mountains, Oklahoma. 



Holotype. — U.S.N.M. No. 108695a; paratype. No. 108695b. 



PLATYCOLPUS HIGHLANDENSIS, new species 

 Plate 6, Figures 30, 31 



This species constitutes another important element of the fauna 

 from the upper beds in the Highland Range, and consequently is 

 described, even though the material is fragmentary. As usual no 

 cranidia are preserved. The pygidium on which this species is based 

 is itself incomplete, but has the normal generic features, and it is of 

 rather large size. As shown in the illustrations the axis is faintly 

 defined, tapering less rapidly than in other species. It is not highly 

 arched in either direction, but has normal distribution of convexity. 



Mendha limestone; (loc. 88) 7 miles north of Bennett Springs, 

 Highland Range, Nevada. 



Holotype.— VS.^M. No. 27017. 



