200 REPORT OP THE Aft[ERICAN COMMITTEE. 
I shoiikl further feel disposed to urge the retention, if possible, 
of the term " primordial fauna," as a legitimate designation for 
the fauna of the Cambrian rocks, in recognition of the eminent 
services of Mr. Barrande in that direction. Of course, if we 
adopt the term Cambrian for the rocks holding the " primordial 
fauna," the latter term becomes unnecessary ; but I should much 
regret seeing it altogether discarded. 
It may well be, however, that between the Acadian group of 
the American Cambrian and the Archean, tliere are beds holding 
a still more ancient fauna, of which there is at present perhaps 
some slight evidence ; and if so, and if further, the fauna of these 
beds should prove sufficiently distinct from that of the Cambrian 
to warrant the placing of the two in different systems, the term 
" primordial fauna " as applied to the fauna of the Cambrian, 
would then, of course, cease to be even paleontologically appro- 
priate. At present, however, the beds in question have been too 
imperfectly explored, it seems to me, to enable us to assert with 
any degree of confidence, that they do not constitute a legitimate 
portion of the Cambrian system. 
Very sincerely yours, 
S. W. Ford. 
Prof. James Hall's Communication. 
Prof. James Hall's communication states : 
" As to your first question as to adopting exclusively European 
terms, I should say, no ! It matters perhaps little what the more 
comprehensive names, as Silurian, Devonian, etc., may be, but 
the lesser terms must be those well-known and well-sustained — 
and among the fossiliferous rocks, by their determined fossils. I 
do not believe that we shall give up any of the American well- 
sustained determinations. I have not the strength to go into this 
discussion just now. * * * 
" In regard to your last inquiry, about the Taconic — were it left 
to me I should say that we drop all the earlier phases of the ques- 
tion, when Emmons was basing his system on the crystalline 
limestone and altered shales, and sifting it clear of tliose earlier 
mistakes, apply the name to the rocks below the Potsdam, accord- 
ing to his conception, but not according to his earlier demonstra- 
tion." 
