84 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



localities in which no cranidia have yet been noted. It is also hoped 

 that further study, particularly of the collections from Loc. i le, will 

 permit the assignment of a pygidium to this head. 



Genotype. — Ptychoparia pernasuta Walcott. 



Range. — Upper Cambrian,- Nevada. 



DOKIMOCEPHALUS GREGORI, new species 



Plate 16, figs. S2, ;^s 



Observations. — This species differs from D. pernasutus in details 

 of the cranidium, the only part available for comparison. A com- 

 parison of figures 29, 30 and 32, 33 of plate 16 shows the stronger 

 occipital ring, broader glabella and shorter frontal limb of D. gregori. 



Formation and locality. — -Upper Cambrian: (lie) : Southwest of 

 Potosi, Missouri. 



DOKIMOCEPHALUS PERNASUTUS (Walcott) 



Plate 16, figs. 29-31 



Ptychoparia ? pernasutus Walcott, 1884, Monogr. U. S. Geol. Surv., Vol. 8, 

 p. 49, pi. ID, figs. 8, 8a, b. (Description and illustration of species.) 



Proampyx ? pernasutus Walcott, 1913, Research in China, Vol. 3, Cambrian 

 Faunas of China, p. 145. (Generic reference.) 



Dokimoccphahis pernasutus Walcott, 1924, Smithsonian Misc. Coll., Vol. 75. 

 No. 2, p. 55, pi. II, fig. I. 



The original description and new figures include what is known of 

 this species. It is a rare form in the Cordilleran area and only one 

 allied species, D. gregori, is known from elsewhere. 



Formation and locality. — Upper Cambrian: (61) Secret Canyon 

 shale. A little north of Hamburg Mine, Eureka District, Nevada. 



Genus DUNDERBERGIA Walcott 



Dundcrbergia Walcott, 1924, Smithsonian Misc. Coll., Vol. 75, No. 2, p. 56. 



Observations. — Dunderbergia was proposed to include a group of 

 species numbering perhaps 20 or more, all formerly assigned to 

 PtycJioparia or closely related genera. The original description of 

 the genotype and the figures of the cranidium and associated pygidium 

 give all that is known of this genus. 



Dunderbergia differs from Modocia in its narrower fixed cheeks, 

 and in the direction of the facial sutures across the frontal border 

 being intramarginal to the center. 



Genotype. — CrepicepJiahis (Loganelhis) nitidus Hall and Whitfield. 



Range. — Upper Cambrian ; Secret Canyon shale, Cordilleran area ; 

 Eureka District, Nevada. 



