60 PALEONTOLOGY OF THE EUEEKA DISTEICT. 



lobe; occipital ring strong, swollen towards the center, and bearing a short 

 spine; occipital furrow well defined; dorsal furrows blended with the de- 

 pressed interior slope of the fixed cheeks and frontal lobe; this causes the 

 glabella to stand out prominently, although but little elevated above the 

 general surface of the head; fixed cheeks rather broad, with a rounded, 

 ridge-like elevation near the eyelobes, and sloping inward to form a de- 

 pressed space before reaching the glabella; eyelobes large, with an ocular 

 ridge running towards the anterior lobe of the glabella; frontal lobe short 

 and. convex, merging into the fixed cheeks laterally, and in front into the 

 strong furrow within the broad, marginal border; the border is convex and 

 swollen at the center into a small protuberance; postero-lateral limbs nar- 

 row and rather depressed. 



Surface finely granulose. 



The identification of the genus Anomocare is made with the illustra- 

 tions given by Angelin, and, until we know more of the structure of the 

 species under consideration, it is difficult to give any other generic refer- 

 ence. No pygidise or remains of the thoracic segments were found in the 

 same association. 



Formation and locality. Cambrian. In a limestone beneath the arena- 

 ceous shales carrying the species of Olenellus, given on a previous page, 

 and associated with 0. Gilberti and 0. Howelli. West slope of Prospect 

 Mountain, Eureka District, Nevada. 



Genus PTYCHASPIS Hall. 



Ptychaspis minuta Whitfieltl (T). 

 Plate x, tig. 23. 



Ptychaspis minuta Whitfield, 1878. Ann. Rep. Wisconsin Geol. Surv., p. 55. Ibid., 

 Geol. Wisconsin, vol. iv, p. 186, pi. i, figs. 25, 26, 1883. 



This is a very minute form, the head measuring only about 3 nn " in 

 length A comparison of the glabella and fixed cheeks, the only parts thus 

 far discovered, with the description of the original type specimens from the 

 Potsdam sandstone of Wisconsin, shows such close resemblances between 

 the two that with our present knowledge it appears impossible to consider 



