40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



of the head, and are larger. The course of the pygidial furrows is 

 also more evenly curved and the border is wider behind the axis. 



Upper Cambrian, Deadwood ; Whitewood Canyon, Deadwood, 

 Black Hills, South Dakota. 



Cotypes. — Univ. Iowa; U.SN.M. no. 93020. 



Pterocephalia bridgei, n. sp. 



Ptcroceplialia saiictisahac Bridge (part), U. S. Geol. Surv. Prnf. Pap. 186-AI, 

 p. 246, pi. 68, figs. 25, 26, 1937. 



This species is characterized by a wide brim, a relatively long 

 glabella, and the curved course of the anterior facial suture. The 

 pygidium assigned to the species has a narrower border than P. 

 sanctisahac, and its rear margin is notched. The surface of the crani- 

 dium behind the eyelines and on the glabella, is nearly smooth. An- 

 terior to these parts the irregular longitudinal folds are rather heavy, 

 and the surface is marked by the usual horizontal, anastomo.sing lines. 



Upper Cambrian, Davis; (loc. iik) near shaft Federal Lead mine 

 no. 4, Flat River, Missouri. 



Holotypc and paratype. — -U.S.N.M. no. 93019. 



Pterocephalia oriens, n. sp. 



Pterocephalia sanctisabac Bridge (part), U. S. Geol. Surv. Prof. Pap. 186-M, 

 p. 246, pi. 68, fig. 24, 1937. 



Associated with P. bridgei is another, possibly smaller, species 

 characterized particularly by its highly elevated palpebral lobes. The 

 eyes are large, and the eyelobes are sharply separated by a deep fur- 

 row. The surface is ornamented similarly to P. bridgei except that the 

 anastomosing lines are heavier. 



Upper Cambrian, Davis; (loc. iik) near shaft Federal Lead mine 

 no. 4, Flat River, Missouri. 



Cotypes.— V.S.^M. no. 96485. 



Pterocephalia potosiensis, n. sp. 



Pferocephalia sanctisahae Bridge (part), U. S. Geol. Surv. Prof. Pap. 186-M, 

 p. 246, pi. 68, fig. 23, 1937. 



Onl}^ a few specimens were obtained in a rather large collection, so 

 that this species seems to be rare. The presence of a large libragene 

 may be interpreted as indicating that P. potosiensis grew to a much 

 larger size than the holotype indicates, or that there is more than 

 one species present. 



P. potosiensis has a wider and longer brim than other Missouri 

 species, but it is shorter than that of P. bridgei. The new species is 



