Correspondence—Dr. F. A. Bather. 523 
Nathorst. Professor Geheimrath H. Rosenbusch could not be present 
to receive his degree. 
Over 470 cards of identification were issued by the Society to 
Fellows, delegates, and guests attending the Centenary. Sixteen 
Foreign Members and 14 Foreign Correspondents, besides many other 
foreign and Colonial visitors, were present. The following were the 
countries represented: Austria- Hungary, Argentine Confederation, 
Belgium, Denmark, Egypt, France, German Empire, Greece, Holland, 
Italy, Japan, Mexico, Norway, Portugal, Russia, Sweden, Switzerland, 
United States, also the Dominion of Canada, India, South Africa, the 
Commonwealth of Australia, and the Dominion of New Zealand. 
CORRESPONDENCE. 
NOMENCLATURE OF AUSTRALIAN SILURIAN OPHIURIDS. 
Srr,—Presumably this heading to Mr. Chapman’s welcome letter 
(Geox. Mae., Oct. 1907, p. 479) does not imply that Silurian Ophiurids 
are to be excepted from the laws of nomenclature when they occur at 
the Antipodes. Yet the difference between us could scarcely have 
arisen had Mr. Chapman felt himself bound by certain rules adopted 
at all recent sessions of the International Congress of Zoologists. But 
he is not even loyal to the Stricklandian code, preferring rather to 
follow ‘an unwritten rule.’ Perusal of the modern code, of which I 
believe Mr. Chapman has now received a copy, will, I hope, show him 
that my remarks concerning Sturtzwra were in simple accordance with 
elementary rules. Itis not my business to defend those rules, but 
since Mr. Chapman assumes that his own views are shared by others, 
I ask leave to put the real point in dispute as clearly as I can. 
The object of selecting a type—whether type-specimen (holotype) 
of a species, or type-species (genotype) of a genus—is, not to indicate 
to one’s readers what one believes to be the most characteristic form 
(norm) of the species or genus under discussion, but to fix on a form 
according to which the species or genus shall stand or fall. Experience 
has taught us that we all make mistakes in our descriptions, and that 
the most carefully constructed diagnosis may prove erroneous. A nomen- 
clature based on diagnoses and on various rational or ethical principles 
has been tried and found wanting. Therefore zoologists have said: 
“We will exclude all these sources of human error from the foundations 
of our nomenclature so far as is possible, and we will base our work on 
concrete specimens.” 
Professor Gregory fixed on Protaster brisingoides as the genotype 
of Sturtzura. His interpretation may have been right or wrong, 
but this at any rate is sure: what P. brisingoides is, the same is 
Sturtzsura; whatever the diagnosis may be, all species congeneric with 
P. brisingoides are also Sturtzura, unless they include the genotype of 
a prior genus. For example, if P. dbrisingoides be congeneric with 
P. sedgwicki, Sturtzura yields to the prior Protaster; but if it be 
