No. 4.] HUNT — ON CAMBRIAN AND SILURIAN. 421 



'' graywacke in Germany" and elsewhere, no conclusions could be 

 drawn from these fossils as to the geological horizon of the rocks 

 in question, [Ibid. II, xxxiii, 371.] In September, 1861, 

 however, Mr. Billings, after an examination of the rocks in ques- 

 tion, pronounced in favor of the later opinion of Emmons, 

 declaring the red sandrock near Highgate Springs, Vermont, 

 containing Conoceplialus and Theca^ to belong to the base of the 

 second fauna " if not indeed a little lower," and to be "some- 

 where near the horizon of the Potsdam." [Ibid. II, xxxii, 232.] 



The dark colored fossiliferous shales which were asserted, both 

 by Adams and by Emmons, to underlie this red sandrock, were, 

 by the former, as we have seen, regarded as belonging to the 

 Hudson-River group, while by the latter they were described as 

 an upper member of the Taconic system ; which was here declared 

 to be unconformably overlaid by the red sandrock, a member of 

 the New York system. These slates, a few years before, had 

 afforded some trilobites, which after remaining in the hands of 

 Prof. Hall for two years or more, were in 1859, described by him 

 in the 12th " Report of the Regents of the University of New 

 York," as Oleuus Thampsoni and 0. Vermontana. He soon 

 however found them to constitute a distinct genus, for which he 

 proposed the name of Barrandia, but finding this name pre- 

 occupied, suggested in 1861, in the 14th "Regents' Report," 

 that of OlcneUus, which was subsequently adopted by Billings, in 

 1865. [Paleozoic Fossils, pages 365, 419.] In 1860, Emmons, 

 in his "Manual of Geology," described the same species, but 

 placed them in the genus Paradoxides, as P. Tliompsoni and P. 

 Vermontana. Hall had already, in 1847, in the first volume of 

 his Paleontology of New York, referred to Olenus the Elllpto- 

 cephalus asajjhoides of Emmons, and also a fragment of another 

 trilobite from Saratoga Lake ; both of which were described as 

 belonging to the Hudson-River group of the New York system, 

 or to a still higher horizon. The reasons for this will appear in 

 the sequel. The EUiptoaphahis, with another trilobite named 

 by Emmons Atops, (referred by Hall to Calymene^ and subse- 

 quently, by Billings to Conocoryplie,') occurs at Greenwich, 

 New York. These were by Emmons, in his essay on the Taconic 

 system ^in 1844), described as characteristic of that system of 

 rocks. 



A copy of the Regent's Report for 1859 having been sent by 

 Billings to Barrande. this eminent paleontologist, in a letter 



