48 PALEONTOLOGY OF THE EUREKA DISTRICT. 
is defined by a scarcely perceptible depression; dorsal furrows broad, well 
defined, and running out in front much broader between the tubercle and 
the fixed cheeks; palpebral lobes rather prominent and situated opposite 
the anterior end of the glabella; postero-lateral limbs long, triangular, and 
marked by a strong furrow within their posterior margin. Facial suture 
directed forward in front of the eyelobes, curving outward a trifle and then 
a little inward on the frontal limb, around the front of which it does not 
appear to extend; back of the eyelobe it extends obliquely outward and 
backward, bending a little more abruptly backward towards the lateral ex- 
tension of the limb, terminating at or just within the genal angle at a dis- 
tance from the dorsal furrow equal in one example to the entire length, and 
in another to two-thirds of the length of the head. 
Surface minutely granulose. 
The specific name is given in honor of Dr. G. Linnarsson, the eminent 
Swedish paleontologist. 
This species is allied to P. Prospectensis, but differs in the position of 
the eyelobes and the larger frontal limb, changes, however, that may be 
only varietal, as there is an interval of 3,000 feet of strata between the 
horizons at which they respectively occur, but for the present they are 
regarded as distinct species. They are strongly marked forms and types of 
a group of the genus not specially recognized heretofore, as they unite the 
presence of a tuberosity in front of the glabella, seen only (with the excep- 
tion of Ptychoparia calymenoides Whitfield) in the eyeless trilobites, Cono- 
coryphe coronatus Barr., C. exsulans Linnarsson, C. Matthewi Hartt, C. Solvensis 
Hicks, C. (Elyx) laticeps Angelin, with the presence of fully-developed eyes 
and the direction of the facial sutures as in Ptychoparia striatus, ete. I am 
not at all certain that P. calymenoides should be included with them, as the 
tuberosity in that species maybe only an unusual thickening of the frontal 
rim of the head and not the true frontal limb, a question not readily deter- 
mined with the specimens thus far obtained 
Formation and locality— Cambrian. Prospect Mountain Group, in the 
upper beds of the Secret Cation shale, on the east side of Secret Canon, 
opposite the Geddes and Bertrand mine, Eureka District, Nevada. 
