Marcou’s Geological: Map. 203 
Our author here takes no notice of one of the most extensive 
limestone formations in the United States, which extends from 
the Helderberg in New York to the Niagara river at Black Rock, 
and thence through Canada West, and forms the higher part of 
Mackinac and the northern part of Michigan proper, or the lower 
peninsular of Michigan. The same limestone extends from 
northern Ohio to ‘Tennessee ; amd though elsewhere noticed, it is 
here omitted in the description of the successive beds or forma- 
tions which constitute the author’s Devonian System. 
Ou page 30, he says, “Since Mr. Agassiz has recognized car- 
boniferous fishes, and Goniatites in the black slate of Ohio, this 
group ought to be placed in the lower carboniferous of which it 
form the base.” Our author has evidently some confused idea 
that the position of the shales and sandstones of Ohio had heen 
a mooted question, aud that it has been settled as above. ‘The 
truth is that Prof. Agassiz has not recognized carboniferous fishes 
slate of Ohio; and those found in the black shale of Indiana 
Were not recognized by Prof. Agassiz. 
_Now Mackinac is a locality of Devonian limestone in part, and 
Yielding very few fossils. ‘he falls of the Ohio consist of Silu- 
"an and Devonian rocks, each yielding a good number of species. 
as fara 
hutian fossil (see page 27, and figure). Our anthor cites Spirifer 
pucronatus. and applies the name to two fignres, both copied 
from Report of New York, one of which is the true species, 
While the other is Spirifer macronotus, a widely distinct species, 
former having a narrow area and strong plications, the latter 
* wide area and numerons fine plications. He is equally unfor- 
inate in his localities, citing New York, Ohio, and ‘Tennessee. 
* Suspect that no other person has seen either of these from 
the two last named localities. 
Spirifer heteroclitus, Def. pl. iii, fig. 7, 7a.—F or this species 
put author has reduced in size two figures of Spirtfer congestus, 
‘om Report 4th, Geol. District of New York, which species differs 
* Widely from Spirifer ‘heteroclitus, that we cannot comprehend 
