NO. 5 UPPER CAMBRIAN TRILOBITES RESSER 9 



gene selected for this species is of ordinary shape and dimensions. 

 The rarely found hypostoma is here preserved. It is characterized by 

 a tumid central lobe and a relatively narrow upturned alate portion. 



The pygidium assigned to the species has a wide axis with three 

 well-defined rings, and stands completely above the pleural platforms. 

 Pleural lobes form an elongate platform which slopes abruptly to the 

 horizontal, slightly thickened border. 



Honey Creek limestone ; (loc. 2,7^) West Timbered Hills, Arbuckle 

 Mountains, Oklahoma. 



Holotype. — U.S.N.M. No. 108636a; paratypes, Nos. io8636b-e. 



CHARIOCEPHALUS ANGUSTATUS, new species 

 Plate i, Figures 35-40 



This is one of the smaller species and in several respects approaches 

 closer to the genotype than most Oklahoma forms. It is represented 

 by several cranidia, together with a pygidium assigned to it. 



The slightly expanded glabella is rather long and has three pairs 

 of furrows visible. It is highly arched transversely. Longitudinally 

 it stands completely above the fixigenes, but the convexity in that 

 direction is confined almost entirely to the anterior fourth. The 

 occipital furrow is exceptionally wide and deep. The brim consists 

 of a simple bar. Pits are present at the anterior angles in the dorsal 

 furrow, which is wide but not as deep as usual. The fixigenes are 

 considerably less than half the glabellar width, and are flatly convex, 

 as a whole sloping only slightly downward from the dorsal furrow. 

 Rather long eyes are bowed most strongly anterior to the middle of 

 the glabella, which causes the species to have the aspect of the 

 genotype. 



The associated pygidium assigned to the species has a moderately 

 high axis and relatively narrow pleural platform. The border is also 

 relatively narrow with slightly thickened edge. 



Honey Creek limestone ; (loc. 37V) West Timbered Hills, Arbuckle 

 Alountains, Oklahoma. 



Holotype. — U.S.N.M. No. 108637a; paratype. No. 108637b. 



CHARIOCEPHALUS GRACILENS, new species 

 Plate i, Figures 29-31 



This is the smallest species in the Wichita Mountains collections, 

 and as far as brim structure is concerned conforms rather closely to 

 the genotype. 



