52 Annals of the Carnegie Museum. 



like that of C. ella Narraway and Raymond were found in the same 

 stratum as the species here described. 



Description. 



Cranidium moderately convex, slightly incurved at the front. Gla- 

 bella flat, obscurely defined, expanding in front of the eyes and extending 

 to the anterior margin; glabellar furrows absent, dorsal furrows present 

 back of the eyes, \'ery shallow. N ck-furrow absent. Eyes of medium 

 size, situated a trifle more than their own length in front of the posterior 

 margin. Behind the eyes there is a small median tubercle on the glabella. 

 Free cheeks rounded at the genal angles. 



Thorax of eight flat segments. Axial lobe a little more than one-third 

 the total width. Pleura with shallow grooves. 



P^gidium rounded in outline, three-fifths as long as wide. Axial lobe 

 obscurely defined, the posterior end usually a little more prominent than 

 the other portions. There are no annulations. The surface is uniforml}' 

 convex, without concave border. 



This species is similar to 0?ichometopus obtnsiis (Hall) of the Chazy, but 

 the shell lacks the very coarse punctje of that form, and there are fewer 

 traces of glabellar furrows. It differs from Onchomctopus suscb (Whitfield) 

 in having a longer pygidium with a narrower and more distinct axial lobe. 



Onchomctopus may be readily distinguished from Isotclus by the presence 

 of a median tubercle on the glabella, the absence of a concave border on 

 both cephalon and pygidium, and by the somewhat narrower axial lobe 

 in the thorax. 



Locality. — This species is quite abundant in the "bufT" limestone, 20 

 feet above the top of the Saint Peter sandstone on Straight River, two 

 miles south of Faribault, Minnesota. A single specimen was found in a 

 quarry at Franklin Forge, Pennsylvania, and donated to the Carnegie 

 Museum by Mr. Ernst W. Greiner. 



Genus Isoteloides Raymond. 

 Isoteloides homalnotoides (Walcott). 



Plate XVI, figures 9-1 1. 



Asaphus homalnotoides Walcott, Advanced Sheets Thirty-first Report New 

 York State Museum, 1877, 20 ; Thirty-first Report New York State Museum, 



1879, 71. — Whitfield, Geology of Wisconsin, IV, 1882, 237, pl. 5, fig. 4. 

 Asaphus Iriangulatus Whitfield, Annual Report Geological Survey of Wisconsin, 



1880, 59. 



