124 Trans. Acad. Sci. of St. Louis. 
held by Tryon, it would seem more natural to regard these 
genera only as the representatives of subfamilies — Pleuro - 
tominae and Haliinae—which alone would compose the 
Pleurotomidae. It is possible, however, if not highly 
probable, that some of the originial subgenera of Tryon, suchas 
Donovania (Lachesis) and Mitromorpha, may really rank 
as subfamilies or even belong to widely different families. 
Probably the course coming nearest to the truth of the 
matter would be to treat the Pleurotomidae in accordance 
with the common practice in equally extensive and complex 
families of arthropods and other classes of animal life, — that 
is to divide the family or subfamily into tribal sections, each 
of which is to be separated into more or less definitely limited 
groups of species which may be known as genera and com- 
prising also, in some special cases, other minor groups or sub- 
genera. The alternative course and the one usually followed 
in the literature of the Mollusca, would be to divide the 
families or subfamilies into a comparatively small number of 
genera, to which a relatively very large number of minor 
groups are to be attached as subgenera. In the latter case I 
find it impossible to scientifically define these supergenera, and 
another objection to this alternative method is that it gives 
rise to too cumbrous a nomenclature. In the present state of 
ignorance of true relationships and exact taxonomic weights 
or values, a name once printed and introduced to nomenclature 
may as well be regarded as the true surname of the species 
as of subordinate value, for a subspecies under the latter con- 
dition must be represented by four words, and, instead of 
adhering to the binomial system, we would be shaping a 
course strongly suggestive of a reversion to the pre-Linnean 
custom of descriptive names or short descriptive diagnoses 
and the manifest advantages of the binomial system would be 
thrown away. It is impossible to devise a system of nomen- 
clature which will serve to indicate at a glance, by the 
form of the names, exactly the weight or value of taxonomic 
relationship or isolation and it may as well not be attempted. 
When we print a tabular statement of species or genera based 
upon structural characters, we do not by any means desire it 
