408 Mr. F. O. P. Cambridge—A Revision 
3. Citation or selection of a type; 4. Selection on account of 
the identity of generic or specific names. We have to consider 
under what circumstances a genus can be regarded as legitt- 
mately restricted either by elimination, by restriction, or by 
the citation of a type. 
(1) To take the case of Pure Elimination first. When a 
genus is subdivided or broken up by an author and one or more 
new genera formed out of the original species, leaving one or 
more species under the original name, this is legitimate elimi- 
nation. But there is no elimination when the original genus 
is merely cited and one or more of the original species cited 
under it. There must be at least one new genus founded 
out of the original species at the time when we claim sub- 
division or elimination to have taken place. 
The reasons for this will be obvious. In the first place, it 
will confine us to works that are definitely systematic, and 
not merely lists; and, secondly, we shall exclude the works 
of those who were merely compiling a popular treatise, 
without any intention of advancing the systematic knowledge 
of the group— Jgnoramuses,” as Dr. Dahl prefers to term 
them. By adopting this course, too, we shall save ourselves 
the trouble of undertaking half a century of research in the 
British Museum, examining every newspaper, periodical, 
magazine, and popular treatise, lest perchance some author 
las unwittingly restricted a genus by some unconscious 
elimination of certain species originally included in it. 
(2) Next, to take the case of “restriction.” When an author 
definitely states that he wishes it to be understood that a 
genus be restricted to such and such species, or cites certain 
species and adds the formula “ sensu restricto,” the conditions 
under which this restriction takes place are in themselves 
a sufficient guarantee that the work is systematéc and not that 
of an ‘ Ignoramus.”’ 
(3) With regard to the third method, namely that of the 
selection or citation of a type, we have to be equally explicit, 
for purely practical purposes, as to the circumstances under 
which such action can be regarded as valid. It is not a 
question as to what early authors meant by the terms “ type” 
or ‘ example,” or what they did not mean ; nor is it a question 
of what we think they meant. They themselves knew, in all 
probability, exactly what they meant by these terms, though 
it is quite clear that we ourselves cannot say for certain what 
they did or did not mean. 
But the practical question for us is, what meaning are we 
going to attach to these terms—typ, typus, type, and 
ca“emplum, exemple, evample? For we must be quite clear in 
