42 Prof. Owen on the Structure of the Teeth of some Fossil Fish. 
like substance ; but this is not true enamel, nor the product of a 
distinct organ ; it differs from the body of the tooth only in the 
greater proportion of the earthy particles, their more minute dif- 
fusion through the gelatinous basis, and the more parallel ar- 
rangement of the calcigerous tubes; but it is developed in and 
by the same matrix, and resulting from the calcification of its 
external layer, is the first part of the tooth which is formed” 
(p. 8). I then go on to cite the fishes that have true enamel, | 
developed from a distinct organ (p.9): and the modifications of 
the enamel-like dentine are described at pp. 34, 54, 56 et pas- 
sim*. To most of the modifications of dentine in fish-teeth I have 
assigned and published names, e. g. ‘osteodentine,’ ‘ vasoden- 
tine,’ ‘ plicidentine,’ ‘ dendrodentine,’ ‘ labyrinthodentine’+: if 
it be really requisite to give a name to the modification of hard 
dentine above defined, I would suggest to Mr, M‘Coy the de- 
sirableness of adhering to the terminology already in use. The 
term ‘ ganoine’ is required for the enamel-like tissue of ganoid 
scales, and that of ‘ vitrodentine’ would have been the one 1 
should have proposed for the tissue which I believe myself to 
have first defined, had I not been checked by the observation. of 
the very gradual passage of hard or true dentine into it in many 
fishes, and by the natural desire to reduce the number of new 
terms to the minimum which the exigences of science seemed to 
- require. 
From the terms of the descriptions quoted from the ‘ Annals 
and Magazine of Natural History,’ 1848, p. 124, and from the © 
‘Proceedings of the Cambridge Philosophical Society’ for June 
1848, anatomists might be led to cite the subject of them as the 
‘ganoine of M‘Coy ;’ but I am sure that gentleman is above the 
device by which small zoologists, of what our plaim-speaking 
German brethren call the ‘ Gattungsmacherei,’ endeavour to ap- 
propriate a new species discovered and defined by another, by 
the mere imposition of a name. 
I remain, Gentlemen, your very obedient servant, 
; RicHarp Owen, 
* The texture of the tooth of Ctenodus is described as presenting “a 
coarse osseous structure at the base, supporting a dense osseous or enamel- 
like layer,” p.63. Although in defining the obvious external characters of 
the tooth of Petalodus the term ‘enamel’ is used, I am careful, in describing” 
the structure, to state that ‘‘the short terminal branches of the medullary 
canals, which distribute the calcigerous tubes to the enamel-like outer layer, 
are slightly bent downwards,” &c., p. 62: so that after the previous defini- 
tion of the ‘ enamel-like’ substance at p. 8, no mistake could be made. 
+ ‘Odontography ’ and ‘ Lectures on Vertebrata,’ tom. i. p, 226. 
