374 LE. Billings on the claim of Priority in the determination 
The only comment that need be made upon all of the above, 
is that at the time Prof. Hall prepared the sections to which 
has appealed, he did not know the age of the Red Sandrock, but 
merely supposed it might consist of the Trenton, Black River 
and Chazy (the limestones of the Mohawk series) in a meta- 
morphic condition. In no place where the Red Sandrock occurs 
is there a vestige of the Potsdam laid down in his sections. 
The fact that he recognized the Potsdam in other places avails 
. him nothing in this discussion. 
I have also lately procured the Geological Report containing 
the letter referred to by Mr. Hitchcock.* It is published as an 
appendix to the Report. The following is a copy of it: 
“ may : 
« Letter from Professor James Hall, on certain fossils in the Red Sandrock of 
| Highgate.” 
rece 
instant, on my return from a geological excursion. I have examined oa 
fossils and, as far as I can determine, they are all of the central pe 
" ( | as 
with several other genera) of our strata, but they belong to Conocephalns 
a! 
its real geological position. The form known to me most like this one, E 
in the Clinton group of this state. I regret. that more species could no 
have been found, or that some form in the preceding strata cou 
obtained to compare with the others already known. me 
The meagre information of the two known species of Conocepha a ; 
likewise an objection to any geological inference from the discovery if 
species. All we know is that they are found in Graywacke, in sheer 
or elsewhere, and the position of the Graywacke is too dubious a” 
quitous to be of any importance in such a case. : nd un 
I regret exceedingly that I am able to give only this meagre ® oe 
satisfactory information, and also that I have not had the satisfacti 
seeing the locality. ee 4 will 
‘Ishall see you in Boston next week, if I am able to go there, a0 
there reply more fully to the other part of your letter respecting New 
York fosssils 
ror ils. g 
 T have prepared nothing for our meeting but am coming to ar 
others do. I am very sincerely yours, &c., James 
epee mia 
see irae ee 
_ * This Journal, [2], xxxii, p. 454. 
