Mr. J. Miers on the genus Witheringia. 141 
case from his ‘Odontography,’ where he had himself. inadver- 
tently called it “enamel” in describing a fossil tooth (Peta- 
lodus), although in other places he had described it as it 
is. Prof. Agassiz I believe, in all his descriptive characters 
has called it “enamel,” and so have most writers. The case 
therefore stands now as before, namely, that a peculiar modifi- 
cation of tissue exists in certain fish-teeth, very different from 
“ enamel,” yet confounded with it by many writers, frequently 
called “ enamel” in the technical descriptions, and for which no 
other term had hitherto been proposed ; my object now is to state, 
that in proposing the term “‘ ganoine”’ for the sake of brevity and 
accuracy in the descriptions of the fossils I was engaged on, I by 
no means intended to impute ignorance of its structural peculi- 
arities to any preceding writer. If I had been aware that Prof. 
Owen had used the word in question orally at his lectures for the 
polished part of ganoid scales, and that he would have preferred 
“ vitro-dentine”’ for the dental tissue, I should of course have 
used it also; but as those terms have not been so published, while 
mine is already current, it is scarcely possible I think to make a 
change now without producing more confusion than the change 
~ would be worth. 
I have the honour to remain, Gentlemen, 
Your most obedient servant, 
Freprricx M‘Coy. 
-XVII.— Contributions to the Botany of South America. 
By Joun Miers, Esq., F.R.S., F.L.S. 
WITHERINGIA. 
Tue following observations will I hope serve to throw some 
light upon this hitherto obscure genus. It always. appeared to 
me that the Witheringia picta, as figured by Martius (Nov. Gen. 
tab. 227), must either form the type of a very distinct group, or 
be considered as a very good illustration of that genus, for which 
reason I refrained from publishing what I had long ago observed 
on the subject, until I could satisfy myself of the absolute cha- 
racter obscurely indicated by L’Heritier, in regard to his typical 
species W. solanacea (Sert. Angl. 33. tab. 1). Under. this un- 
certainty (in a note, Lond. Journ. Bot. iv. 353) [alluded to the 
unsuccessful search I had everywhere made for some specimen, or 
better details, of the plant in question, so as to be able to com- 
prehend the limits and features of the generic character of 
Witheringia, and I expressed my regret that the original type no 
longer existed in L’Heritier’s herbarium in the British Museum, 
as that would at once have cleared up this ambiguity. Dr. 
