200 The JVew York System., [Oct., 



from the type, although the age may be that of the Sihirian of 

 England. 



In this country we have unquestionably Silurian rocks, and 

 many undoubtedly will use the name exclusively; still we may 

 be allowed to suggest that where considerable difference of litho- 

 logical constitution and of the distribution of fossils exists, wheth- 

 er it may not be better after all to employ some other term as a 

 name for the system. In New York it has been often said that 

 the Silurian is well developed. This is probably true; perhaps 

 better developed or more suitable for the type of this series of 

 formations and of this period, than that of Siluria itself. In con- 

 sequence of the great differences which exist in the New York 

 series and Silurian, we believe that the former has a preference 

 to the latter. The difference may be summed up thus: 1st. It is 

 more expanded downwards, that is, it has important rocks unknown 

 to the system in England. 2d. It has important members in other 

 parts of it unknown in England. And 3d, very few of the fos- 

 sils belong to the same species; they are principally analoQ"ous 

 forms, being related to those of Siluria, as our living molusks are 

 to those of Europe. We prefer for these reasons the name New 

 York system to Silurian system, and as there can be no doubt of 

 the succession of these rocks, we believe the name may be ap- 

 plied with propriety to the rocks of the same age in other parts 

 of this country. The question w^ill unavoidably come up, where 

 shall the line of demarcation be drawn between the New York 

 and the adjacent systems? After a careful examination of the 

 question, w^e feel quite confident that it might be extended in this 

 country so as to include the Catskill division, or to extend to 

 the carboniferous limestone. We have no very good dividing 

 lines till we reach the base of the carboniferous. It is true that 

 we find a few fish in this country, in the inferior part of the Cats- 

 kill, or old red sandstone of Europe. But the molusks and conchi- 

 fers belong to the same types as those below. The series is a 

 continuous deposit here of similar matter, the succession of which 

 is scarcely broken by conglomerates or disturbances of much im- 

 portance. The extension of the New York system as proposed, 



