238 E. Billings on the Genus Centronella. 
to the figures which he misinterprets. The only question (in 
this connection) that can be of any interest to men of science is 
this.—TIs there in nature a genus of fossil Brachiopods having the 
general structure assigned to Centronella by me in 1854? The dis- 
coveries of Prof. Winchell, Dr. Rominger and myself prove very 
clearly that there is, and I think I have a right to point out that 
Prof. Hall’s recently published observations have added nothing 
but words to these discoveries. 
served by shifting it to another genus. 
It will be observed that the new edition of the genus in Prof. 
Hall’s paper (p. 401) is in fact founded on the loop of Centronella 
Julia. e have no evidence that this species is congenerie with 
those which were made the typical forms in 1861. ‘There is 10 
connection yet shown between the Cryptonella of 1861 and the 
Cryptonelia of 18638. 
I repeat that the genus Cryptonella can be sustained only by 
showing that the internal organs of the species upon which it 
was oon aaerge 8 founded are different from shoae of all prevent 
established genera. As these organs have never been seen, — 
that is known of the genus is expressed in the short description 
which I have given above in two lines. I do not say that it 18 
not a new genus, but only, that we have as yet no published 
proof that it is, 
e question whether C. Julia belongs to the genus Centro- 
nella is one of some importance, as its solution depends 8 
certain principles of classification much discussed of late. That 
our genera are founded on the modifications of the ultimate parts 
of animals, there can be no doubt; but how great an amount of 
modification is required to constitute a generic character 18 4 
