42 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



Upper Cambrian, Honey Creek; (loc. Sgv) 4 miles south of Hen- 

 nepin, west Timbered Hills, Arbuckle Mountains, Oklahoma. 

 //o/oh'/T.— U.S.N.M. no. 93017. 



PTEROCEPHALINA, n. gen. 



For many years the genotype has been referred from one genus to 

 another, which, besides those listed below, include Anomocare, Niohe, 

 Saukia, and Platycolpus. The pygidium resembles that of both 

 PterocephaUa and the Saukinae but does not fit into either. Careful 

 search of the collections has revealed a partial cranidium which also 

 has affinities with PterocephaUa but cannot be placed in that genus. 



Pterocephalina is characterized by a broad bordered pygidium in 

 which the wide doublure is almost severed by the deep notch in the 

 rear margin of the tail. The axis, which is subcylindrical, extends 

 almost to this notch, being connected with it by a sharp postaxial ridge. 

 Unexfoliated specimens show that pleural fusion is far advanced, 

 but the furrows are traceable on the upper surface nearly to the border. 

 The holotype shows the underside and hence the extent of the doublure, 

 but not the pleural furrows. 



The cranidium assigned to the species is incomplete. It consists of 

 a large prominent, highly arched glabella, on which the rear pair of 

 furrows are represented by slight, rearward directed indentations. 

 Eyelines present. Eyes evidently of moderate size. Fixigenes less 

 than half glabellar width. Brim very wide, apparently with a flat, 

 sharply upturned rim. Wide preglabellar area is striated by coarse 

 irregular lines among which are interspersed scattered lumps. The 

 entire cranidium is highly arched in both directions. 



Genotype. — Dikellocephalus bilobatus Hall and Whitfield. 



Pterocephalina bilobata (Hall and Whitfield) 



Dikelloceplialiis [Ptcroccfhaliis] bilobatus Hall and Whitfield, U. S. Geol. 



Expl. 40th Par., vol. 4, p. 226, pi. 2, fig. 36, 1877. 

 DicellocepJialus bilobatus Walcott, U. S. Geol. Surv. Mon. 8, p. 40, 1884. 

 Platycolpus bilobatus Walcott, Smithsonian Misc. Coll., vol. 57, no. 13, p. 349, 



1914. 



Upper Cambrian, Secret Canyon ; (loc. 65) east side Sierra Canyon, 

 opposite Pinnacle Peak, and (loc. 61) south of Hamburg Mine, Eureka 

 District, Nevada. 



Holotype.— U.S. ISl.M. no. 24568. 



