98 Geological Survey of the State of New York. 
The opinions concerning the age and place in the general series 
occupied by the rocks of central and western New York, have 
been at variance. They have been alternately described as transi- 
tion and secondary ; again the saliferous group is counted as above 
the coal series, and this, with the sandstone of Rochester regarded 
as the “‘new red ;” and “ the rocks of the 4th district are consid- 
ered (Report for 1838) as belonging to the old red sandstone and 
the carboniferous groups, and to be above the Silurian system of 
Mr. Murchison,” a conclusion “based in part upon the organic 
remains.” The gradual and imperfect development of Murchi- 
son’s labors before the publication of his work on the Silurian 
system, afforded few exact means of identifying distant strata, 
but since his magnificent work is now in our hands, an extend- 
ed comparison by Mr. Conrad* of the organic remains of the New 
- York rocks, has enabled him to class them as equivalents of the 
Silurian, and the rocks from the Trenton limestone to the Moscow 
shales and the sandstone and shales of Cazenovia inclusive, he 
identifies.as members of this system, and he finds, as at Bloss- 
burg, Tioga County, Penn., the old red sandstone in its proper po- 
sition between the coal and Silurian rocks, of the same color and 
character, mineral and fossil, as that of England, while some of 
the earlier rocks on the Hudson and Mohawk are regarded as 
equivalent to the Cambrian. Should this classification be sustain- 
ed, it is very desirable that in the summary of the work some sys- 
tematic or uniform nomenclature of the rocks should be adopted. 
The paleontologist, Mr. Conrad, describes several new species 
of fossils, and as the names of some of the genera are new to 
many American readers, the reasons given for their use by Maur- 
chison, Part II, p. 643, are here extracted. 
‘“The generic names of Leptena, Airypa, and Orthis, being new 
to English geologists, their use on this occasion, demands an ex- 
planation. They are in fact, subdivisions of the great family of 
Lerebratula, which, having been established by Dalman, have 
been since adopted by many foreign authors; and Mr. J. de C. 
Sowerby gives the following reasons for sanctioning their in- 
troduction among us. ia 
“The generic names Leptena, Atrypa, and Orthis, have been 
adopted from Dalman’s memoirs in the Stockholm Transactions, 
tg se aes * See this Journal, Vol. xxxviu, p, 86. 
