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 Ptyclioparia 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 Ptyclioparia striatus, etc. I am 

 not at all certain that P. calymenoides should be included with them, as the 

 tuberosity in that species may be only an unusual thickening of the frontal 

 rim of the head and not the true frontal limb, a question not readity deter- 

 mined with the specimens thus far obtained 



Formation and locality. Cambrian. Prospect Mountain Group, in the 

 upper beds of the Secret Canon shale, on the east side of Secret Canon, 

 opposite the Geddes and Bertrand mine, Eureka District, Nevada. 



