5 UPPER SILURIAN AND DEVONIAN OF NORTH AMERICA. 
entertained, it has been at once dispelled by the collections brought to England 
by Mr. Lyell, and submitted by him to our examination, whilst he was preparing 
for the public eye a work and map, in which the parallelism of the American with 
the British succession will be clearly pointed out. Notwithstanding the number 
and variety of new forms peculiar to that continent, we there find a sufficient 
number of species, either identical with, or closely allied to those of Europe, to 
enable us to recognise the development of the same series of phenomena. There, 
for example, as is the case in Russia, the most ancient mollusca are Brachiopods, 
void of an articulated hinge, and provided with a horny shell. The lower sand- 
stone of the tracts near Lake Champlain, so copiously charged with fragments of 
Lingulae, that they mark the lamination of the rock, and almost give to it a 
micaceous aspect, are therefore strikingly analogous to what has been described 
as the Ungulite grit of St. Petersburgh 1 . Above the sandstones occur the Trenton 
and blue limestones, fully developed in North America, and charged with Trilo- 
bites characteristic of strata of the same age in Northern Europe. Among these 
Trilobites we have but to name Illamus crassicauda and Asaphus expansus , with 
Trinucleus and Isotelus, to show at once how these forms represent the most nu- 
merous and characteristic species of the Lower Silurian strata of Northern Europe. 
Such also is the position of that most decisive coral the CJuctetes (Favosites) Petro- 
politanus and of the shell Spirifer lynx, the varieties of which, abundantly diffused 
through the states of Ohio, Tennessee, Kentucky and Indiana, occupy exactly 
the same geological position as in Russia and Scandinavia. Lastly, besides certain 
Graptolites, this lower stage terminates, in ascending order, with a calcareous band 
volume, the mere inspection of which led us at once to infer, that in the vast series which he simply de- 
signates the “ New York System.,” the Devonian, Upper Silurian and Lower Silurian rocks are clearly to 
he distinguished. It is somewhat remarkable that the Ludlowv ille rock of this author seems to be the 
exact equivalent of the Ludlow rocks of England ! So numerous is the list of American authors who have 
w'ritten on the older rocks of their respective states, that we cannot now mention, still less do them justice ; 
though we must not omit to notice Professor Hitchcock, who so fully described the geology of Massa- 
chussets, and Dr. Green, whose monograph on the Trilobites, published some years ago, clearly indicated 
the existence of Silurian rocks in that country. Nor can we conclude this note without stating, that in 
addition to a previous general application of English classification to the chief sedimentary deposits of the 
United States, Mr. Featherstonhaugli placed in a general way the lower strata of the Alleghany chain on 
the parallel of the Silurian system as early as the year 1836. 
1 See Proc. Geol. Soc. of London, abstract of Memoirs read in April 1842, at which time the authors 
of this work had not drawn the true distinctions between the Lower and Upper Silurian rocks of Russia. 
Pander’s Beitriige, and Chapter III. of this work. 
