I 



NO. 22 CAMBRIAN TRILOBITES, 3D CONTRIBUTION RESSER II 



Elrathia dubia, n. sp. 



Ptychoparia permulta Walcott (part), Smithsonian Misc. Coll., vol. 67, no. 4, 

 p. 145, pi. 21, fig. 2, 1918. 



This specimen departs in several respects from the typical forms 

 of the genus, even though some features relate it to E. permulta. The 

 new species lacks eye lines and is narrower between the eyes. The 

 surface is granulated instead of being striated, and the granules 

 behind the eye-line position both on the glabella and the fixigenes are 

 heavier than they are anterior to that position. 



Undescribed species have combinations of the surface markings of 

 E. permulta and E. dubia, which is a strong reason for retaining the 

 latter in the genus. 



Occurrence same as preceding. 



Holotype. — U.S.N.M. no. 65517. 



ELRATHINA, n. gen. 



A group of species considerably like Elrathia at first glance presents 

 uniformly different characteristics, so that another genus must be 

 recognized. In general the trilobites of both groups are similar, par- 

 ticularly in appearance. Elrathina has a smaller pygidium which 

 further differs in structure. No great difference is apparent in the 

 cranidium, except the narrower preglabellar area. The thorax, owing 

 to more numerous segments and the necessity of tapering to a smaller 

 tail, becomes more triangular in shape and therefore looks somewhat 

 different. 



Genotype.— C 0110c ephalites cordillerae Rominger. 



Elrathina cordillerae (Rominger) 

 Conocephalites cordillerae Rominger, Proc. Acad. Nat. Sci. Philadelphia, p. 17, 



pi. I, fig. 7, 1887. 

 Ptychoparia cordillerae Walcott, Amer. Journ. Sci., 3d ser., vol. 36, p. 165, 

 1888; Smithsonian Misc. Coll., vol. 67, no. 4, p. 144, pi. 21, figs. 4 

 (3 and 5?). ipiS. 

 Middle Cambrian, Stephen; (loc. 14s) Mount Stephen, above Field, 

 British Columbia. 



Holotype.— AcsLd. Nat. Sci. Philadelphia; cast, U.S.N.M. no. 

 17831 ; plesiotypes, nos. 65518, 57658. 



ELVINIA Walcott, 1924 



Elvinia unisulcata (Hall and Whitfield) 



Crepicephalus (Loganellus) nnisulcatus Hall and Whitfieij), U. S. Geol. 



Expl. Par., vol. 4, p. 216, pi. 2, figs. 22, 23, 1877- 

 Ptychoparia unisulcafus Walcott, U. S. Geol. Surv. Mon. 8, p. 58, 1884. 



