140 On the Ganoine of some Fish-teeth. — 
on the part of Agassiz of the structure which I have pointed out 
in my paper; and it also shows the author’s interpretation of - 
what portion of rays are seen above the spine in fig. 1. pl. 18. 
of the Monog. of the Old Red Fishes, which Sir P. Egerton 
states to be a good representation of the structure (although 
he does not mention that fig. 2 of the same plate represents it 
as perfectly heterocercal). Will Sir Philip Egerton compare 
Agassiz’s restored figure referred to, with mine in your Journal, 
and say that that is right and mine wrong? or will he say that 
his figure and the above portion of the quotation are not as 
clear definitions of the heterocercal type of tail as it is possible 
to give? I trust these observations will show, that whatever 
“unfairness ” may be in this discussion is not on my side; and 
I may assure Sir Philip Egerton, that not for all the palzontolo- 
gical discoveries in the world would I misrepresent the writings 
of any one, much less of Prof. Agassiz, for whose brilliant talents, 
extensive learning, and enormous service to natural science, no 
one can have a more profound veneration than myself. 
With regard to my “ using the cancelled specific appellation 
latus when speaking of the Coccosteus decipiens,” I must beg to 
refer Sir Philip Egerton to the Rules for Nomenclature published 
by the British Association for the Advancement of Science, for 
the reasons which have influenced me in retaining the original 
name. I have the honour to remain, Gentlemen, 
Your most obedient servant, 
Freperick M‘Coy. 
XVI.—Reply to Prof. Owen’s Letter on the Ganoine of some Fish- 
teeth. By Frepmricx M‘Coy, M.G.S. & N.H.8.D. &e. - 
To the Editors of the Annals of Natural History. 
GENTLEMEN, Cambridge, Jan. 13th, 1849. 
In reference to Prof. Owen’s letter in your last Number, will you 
favour me by the insertion of a few lines ? | | 
In your Number for August last, I published a notice of some 
fossil fish, and in describing the teeth used the new term “ ga- 
noine” to designate a peculiar modification of ‘ dentine,” which, 
from forming the hard polished surface of those teeth, had been 
confounded with true enamel by nearly all writers on fossil fish. 
To define the term, I briefly defined the tissue for which I used _ 
it, and its anatomical distinction from “enamel.” Prof. Owen. 
writes to point out that he had observed the distinction himself, | 
as indeed every anatomist must who looks at a slice of tooth 
through a microscope; yet in the note to his letter he cites a 
