232 PROCEEDINGS OF THE AMERICAN ACADEMY 



A very thick solid mass of conglomerates, micaceous shales, and 

 specially quartzite, of at least 1,500 feet, without fossils, rests upon the 

 granite which is visible at but one point; this group is called "Pros- 

 pect Mountain (piartzite." (All the names of groups given by Messrs. 

 Walcott and Hague are names peculiar to the n-giou of Nevada and 

 Eureka.) This group without fossils corresponds stratigraphically to 

 the " St. Albans Group." 



Directly above is the " Prospect Mountain limestone," which begins 

 by a bed, 100 feet thick, of shales with Olenelli. The authors have 

 united aud confounded this very important horizon of the zone of 

 Olenelli with a great mass of limestone, from which it is doubly dis- 

 tinct, — first by its lithology, and secondly by its palaeontology. I 

 have shown this on the section by a line. In these shales tliere are 

 three species of Olcnelhis, a Conocephalltes, and a bi-achiopod Acrotreta. 

 This little fauna corresponds so well with that of Georgia, that it is 

 needless to insist on the affinities which connect them. So the zone 

 with Olenelli, or " Georgia slates," are strongly marked in Nevada. 

 Above are 500 feet of bluish limestone without fossils. Then we 

 come to a horizon of fossils belonging to the genera DikelocejjJtalus, 

 Conocrplialifes, and Affnostus. Higher up is an enormous mass of 

 2,000 feet of metamorphosed and broken up limestone without fossils ; 

 and the last 300 feet, at the upper part, containing quite a large num- 

 ber of fossils belonging to the genera Dikelcmejjhalus, Crepicephalus, 

 Conocephaliies, Oxygia, Agnostus, Orf/iis, Lingula. Obolella, etc. On 

 the whole, a fauna resembling that of Point Levis in Canada, aud 

 already Supra-Primordial. 



Then comes a mass of slates 1,600 feet thick, without fossils, or 

 having only imperfect traces of fossils badly pn'served, called " Se- 

 cret Cailon shale." 



At the top of this group are the " Hamburg limestones," 1 .200 feet 

 thick, with numerous fossils, belonging to the genera Dikelocephalus, 

 Crepicephalus, Conocephalltes, Oxygia, Agnostus, HyoUthes, Kutorgina, 

 Iphidea, Lingula, Lingulrpis, etc., — a fauna having all the characters 

 of the Supra-Primordial. 



Then come 350 feet of the " Hamburg shale," with a fauna 

 almost identical with the preceding one in genera and species ; the 

 whole is really but one group, the " Hamburg Group," which, added to 

 the " Secret Canon shale," and to the " Prospect Mountain lime- 

 stone," from which we must take 100 feet at the base where are the 

 "Georgia slates" with 0/e?ic//t, represents in Nevada the '"Phillips- 

 burgh aud Point Levis Group " of Vermont and Canada. At Eureka 



