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Professor Agassiz on the Distribution of Fossils. 9 
a kind of ringing sound, produced by the successive reper- 
cussions of the sonorous waves by the banks. 
My experiments on the possibility of hearing an echo re- 
flected by the bottom, are not yet sufficiently numerous to 
enable me to decide on the efficacy of this means of measuring 
the depth of water. 
New Views regarding the Distribution of Fossils in Formations. 
By Professor Acasstz. With Observations, by Professor 
Bronn. 
_ I pousr much if any one possesses such ample materials as 
I do, for judging of the limits of the species of Trigonia de- 
seribed in my Monograph. I have employed these with scien- 
tifie care, without regard to prevalent opinions, and have ex- 
pressed candidly the result to which they have led me, viz. 
that no species occurs in two geological formations—nay, not 
even in two different parts of one formation ; and I have the 
more confidence in this conclusion, because I have invariably 
found it confirmed by fossil fishes and echinodermata. The 
question as to the extension of the boundaries of a species does 
not come into consideration here; for the differences ascer- 
tained to exist between specimens from two localities—it 
matters not whether they belong to one or to two different 
formations—remain for ever the same, whether they can be 
perceived easily or with difficulty, and whether the individuals 
be thrown together under the same label, or kept distinct. In 
order to express my conviction as to species, I state the follow- 
ing to be my opinion: That no so-termed character—that is, 
no observable mark—can be so striking as to indicate an abso- 
lute specific distinction ; but, at the same time, it should never 
be regarded as so trifling as to point to absolute identity ; that 
characters do not mark off species, but that the combined rela- 
tions to the external world in all circumstances of life do. Thus, 
I believe I am able to shew that many organic beings are spe- 
cifically distinct,—or, at least, that they stand in no genealo- 
gical relations to one another,—although the individuals are 
so like as to be confounded. On the other hand, it is known 
VOL. XXXII. NO. Lx1t.—sanuary 1842. G 
