XV.] CAMBRIAN AND SILURIAN IN NOETH AMERICA. 419 



up to the base of the Carboniferous, for which Dawson has sug- 

 gested the more appropriate name of Erian. (See further the 

 author on Breaks in the American Palaeozoic Series, and Hall 

 on the Relations of the Niagara and Lower Helderberg For- 

 mations, Proc. American Association for the Advancement of 

 Science, 1873, pages 118 and 321.) 



[The name of Middle Silurian, applied by Billings to the 

 group holding the Medina-Niagara fauna, should be rejected, 

 for the reason that the group below it has no just title to the 

 name of Lower Silurian, but is Upper Cambrian. The two 

 distinct faunas included in the true Silurian rocks might with 

 great propriety be distinguished as Lower and Upper Silurian.] 



The history of the introduction of the names of Silurian 

 and Devonian into North American geology now demands our 

 notice. Professor James Hall, as we have seen, while recog- 

 nizing in the rocks of the New York system the representatives 

 alike of the British Cambrian, Silurian, and Devonian, wisely 

 refrained from adopting this nomenclature, drawn from a region 

 where wide diversities of opinion and controversies existed as 

 to the value and significance of these divisions. Lyell, how- 

 ever, in the account of his first journey to the United States, 

 published in 1845, applied the terms Lower and Upper Silu- 

 rian and Devonian to our palaeozoic rocks. Later, in 1846, De 

 Yerneuil, the friend and the colleague of Murchison in his 

 Russian researches, visited the United States, and on his return 

 to France, published, in 1847 (Bui. Soc. Geol. de Fr., II. iv, 

 12, 646), an elaborate comparison between the European palae- 

 ozoic deposits and those of North America, as made known by 

 Hall and others. He proposed to group the whole of the rocks 

 of the New York system, up to the summit of the Hudson 

 River group, in the Lower Silurian, and the succeeding 

 members, including the Lower Helderberg and the overlying 

 Oriskany, in the Upper Silurian ; the remaining formations to 

 the base of the Carboniferous system being called Devonian. 

 This essay by De Yerneuil was translated and abridged by 

 Professor Hall, and published by him in the American Journal 

 of Science (II. v, 176, 359 ; vii, 45, 218), with critical remarks, 



