54 PALEONTOLOGY OF THE EUREKA DISTRICT. 



Ptychoparia (Euloina ?) affinis, n. sp. 

 Plate x, fig. 12. 



General form and appearance much like that of P. similis, but differing 

 in its more pronounced convexity, in the more deeply impressed two poste- 

 rior pairs of glabellar furrows and the rounded marginal rim instead of the 

 long planulate margin ; features that render the two very distinct. Surface 

 finely pustulose. Mr. E. Billings has described an allied form from Canada 

 as Menocephalus Sedgwicki, the generic reference of which is very doubtful. 



Formations and localities. Cambrian and Silurian. In the limestones or 

 passage beds between the Prospect Mountain and Pogonip Groups above 

 the Hamburg belt of shale east of the Hamburg mine, and in the lime- 

 stone of a little higher horizon northeast of Adams Hill, Eureka District, 

 Nevada. 



Ptychoparia laeviceps, n. sp. 

 Plate x, figs. 17, 18. 



General form of head within the facial sutures subtrapezoidal. Glabella 

 conical, strongly convex, with very faintly defined dorsal furrows separat- 

 ing- it from the rapidly sloping fixed cheeks ; two pairs of furrows are just 

 discernible by slight impressions on the surface ; occipital ring strong, 

 rounded, separated from the glabella by a shallow furrow ; fixed cheeks of 

 medium width, sloping rapidly down from the glabella and from the small 

 eyelobe, situated a little back of the center, to the front and back; frontal 

 limb short,' convex, and depressed to the broadly rounded, strong, marginal 

 rim; postero-lateral limbs rather strong and running out beyond the line of 

 the lateral extension of the frontal limb. 



Surface smooth to the unaided eye ; under a strong magnifying power, 

 minutely granulose. 



This species is peculiar in the absence of strongly marked furrows and 

 the general smooth appearance, as though all strong outlines had been 

 removed by rubbing off the outer surfaces. In form it resembles the follow- 

 ing species and is closely allied to it. It differs from it in the general ap- 

 pearance and also in the course of the facial sutures in front of the eyes. 



