LOWER PALEOZOIC. 207 
Orclovician System. 
( Hudson river shales. 
Upper Ordovician (Hudson Group), | ^tica shales. 
r Trenton limestone. 
Tir-jji r\ J • ' rn^ i n \ ! Black river limestone. 
Middle Ordovician (Trenton Group), -^ ^. , 
I Birdseye limestone. 
L Chazy limestone. 
f Calciferous sand rock. 
Lower Ordovician (Potsdam Group), j p f . i • d t 
Cambrian System. 
Upper Cambrian, Taconic group. 
Middle Cambrian, St. John's group. 
Lower Cambrian, Ocoee group ( ? ). 
Other Opinions. 
Besides these communications, a number of answers have been 
referred to the sub-committee on the Lower Paleozoic, given in 
response to the questions O, P, Q, of Dr. Frazer. In addition 
to those who have already been quoted at length, the following 
geologists give opinions on the nomenclature of the Lower Paleo- 
zoic, viz. : Sir William Dawson, Dr. A. R. C. Selwyn, Profes- 
sors Le Conte, Irving, G. H. Williams, and B. K. Emerson, 
and Messrs. Hague, Blake, Macfarlane, S. F. Emmons, and 
Dutton. 
Of these opinions, so far as they relate to the use of the term 
Taconic, Messrs. Dawson, Selwyn, and Irving think that the 
term is utterly useless in geological nomenclature. Messrs. Em- 
mons and Emerson say they would follow the conclusions of Mr. 
Walcott. Messrs. Williams and Le Conte recommend that the 
term be not used at present, owing to the controversy and con- 
fusion attending it. Hague and Blake suggest that it be applied 
to the strata to which it belongs; and Blake strongly insists upon 
it. Macfarlane would apply it to some "Pre- Cambrian" rocks, 
as the schistes azoiques ; and Dutton thinks its value, is still "an 
open question." 
Other answers given by the same gentlemen relate to the 
manner of division of the " Cambrian," viz. : Professor Dana 
suggests that the terra Cambrian could properly be made to 
cover all that Sedgwick included under the term, as proposed by 
some British geologists ; that is, the rocks of the first and second 
