No. 275.] 
61 
vania and Virginia, and is more generally known than any other spe- 
cies. It is absolutely limited to this peculiar formation, serving to 
identify it in every locality. It appears to have formed a net-work, 
like the Dictuolites, but terminating in some of its ramifications unlike 
the latter, in fasciculi, somewhat resembling the human fingers. It is 
very diflScult to ascertain with certainty whether the branches really 
anastomose, but such is the opinion derived from a careful examination 
of some very perfect specimens. 
It is doubtful whether a more perfect series of Transition strata than 
that of New- York can be found in any part of the world, and certainly 
no group or system is more perfectly characterized by peculiar forms of 
organic remains. Nine distinct groups occur within the limits of the 
State, all below the great coal formation and Carboniferous or mountain 
limestone strata, which lie in the bordering counties of Pennsylvania. To 
show the order of superposition of some of the transition rocks, and 
the distinctive nature of the organic remains, I have drawn up the fol- 
lowing table, chiefly from observations made during the first year of the 
survey, and confirmed by subsequent examinations. 
