Victorian FossiU, Part XII. 321 



tuberculate surface, as the Crfpicephalus. pygidium ; and the 

 darker-coloured fragments, as compared with those of Ftycho- 

 imria, exactly correspond. 



Affinities. — At first sight the cranidia j^rovisionally referred 

 to the aboA'e genus and species, might be mistaken for a form 

 like S phaeroiJhthalmus alatus, Boeck sp.^ (=: Olenus humilis, 

 Phillips) ; but there is no deeply marked basal furrow on the 

 glabella corresponding to forms of that genus. R. P. Whitfield 

 has described and figured the cranidium of a species of Crepi- 

 cepliahis"^ which shows all the fundamental characters of the 

 form here dealt with. He also gives a profile view of the same 

 form, and its resemblance to ours is even more striking than 

 the superficial view. The glabella of our trilobite is more 

 decidedly globose than in Whitfield's species, which, although 

 highly convex, is broadly conical ; but in both forms the an- 

 terior border and the deep neck furrow are similar in character. 

 The fixed cheeks, moreover, are larger in our species. Creiii- 

 Cfphatuii onusti/s, Whitfield, occurs in the Potsdam Sandstone 

 (Upper Cambrian) of Wisconsin, L.S.A. 



The pygidium hei'e regarded as the holotype of the above 

 species shows a remarkable resemblance to that figured as 

 Cr-epirephalus liliana, Waloott, from the Middle Cambrian of 

 Nevada, U.S.A." That species is of slender proportions, and 

 I he tail spines are less divergent than is indicated in our 

 specimen. The two forms agree in the rounded shape and 

 almost even width of the axial lobe, and in having a deep in- 

 cision between the last and penultimate suture-line of the 

 anterior region. 



This genus occurs throughout the Upper Cambrian in North 

 America. Tlie genotype, according to C. D. Walcott^ is Crepi- 

 cephcdu-'i iowensis, Owen sp. '' It is a characteristic fossil of 



1 Tnlobites alatus, Boeck, 18.38, Goea Norwegica, I., p. 143,' 01. (Sph.) humilis, Phillips 

 1848, Mem. Geol. Sjirv. Gt. Brit., vol. ii., pt. 1, p. .55, woodcuts figs. 4, ii, 6. 



2 C. onuxtus, Whitfield. Geol. of Wisconsin Survey of 1873-9, vol. iv., 1882, p. 182, 

 pi. i., figs. 22. 23. 



3 " Second Contr. to the Studies on the Cambrian Kaunas ot N. Ainrrica." Bull. U.Sl 

 Geol. Sun., No. 30, p. 207, pi. xxviii., fi<js. 3, 9a-c. 



4 Op. supra cit., p. 206. 



h Diki'locepkfiluti (';) iowensin, Owen. Geol. Rep. of Wisconsin, Iowa and Miiniesota, 

 18,52, p. .575, pi. i., fi<r. 4. Ptpchvparia (Crepicephalus) iowensist, Owen sp., C. D. Wall- 

 cott, Bull. U.S. Geol. Surv., 1884, No. 10, p. 36, pi. vi., fig. 2, 2a. 



7 



