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 said 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 palaeontologist, 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 Mur- 

 chison, Part il, p. 643, are here extracted. 



"The generic names of Leptmia, Atrypa, 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 

 Terebratula, 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. 



" The generic names Leptcena, Atrypa, and Orthis, have been 

 adopted from Dalman's memoirs in the Stockholm Transactions, 



* See this Journal, Vol. xxxviii, p. 86. 



