United States National Museum - si-pddr - Smithsonian Institution

6 BULLETIN 112, UNITED STATES NATIONAL MUSEUM.
A few Mediterranean forms such as Gibbula adriatica and C'ymatium
corrugatum appear in the Californian fauna, but no plausible
explanation of their presence occurs to me.
Certain discrepancies between the groups of mollusks both in deep
and shallow water on the two sides of America were pointed out by
me in the discussion of the data in my reports on the dredgings of
the Blake and Albatross. For instance the profusion of species of
the Marginellidae in West Indian waters and their scarcity on the
Pacific side. Some genera are found only fossil on the Atlantic
shores, such as Strombina, Harpa, and Cymia, but are well repre-
sented by living forms in the Pacific. Again note the profusion of
Haliotis on the shores of the Pacific with only a single depauperate
deep water species in the western Atlantic. The great number of
Pacific Tritonalia and other muricoid species contrasts strongly with
their paucity on the opposite shores. The late Dr. Philip Carpenter
used to lament the absence on the Atlantic coast of the myriads of
minute Gastropods he was accustomed to collect on British hunting
grounds. That the difference is real, is proved by the scanty rewards
which have fallen to New England collectors. But no such scarcity
would have been noted had Doctor Carpenter been a west coast
collector.
These singularities of distribution will doubtless find an explana-
tion when the recent and fossil mollusk faunas of the two areas are
more thoroughly known. At present, hypotheses must be regarded
as premature.
A few remarks on the classification adopted may be in order. Of
late years some specialists on particular groups, having small knowl-
edge of any but their own particular field, have naturally exaggerated
the importance in a classificatory sense of certain features of the
subjects of their studies. Two or three bristles in a particular place
have sufficed to establish a dipteran genus. This sort of taxonomy
does not appeal to me and I have, except in extremely populous
groups where convenience requires more laxity, endeavored to exercise
a reasonable conservatism in the adoption of divisional names
of higher rank than species. I have preferred to utilize the sub-
generic names in groups containing numerous species because it
familiarizes the student with the subdivisions Avhich in many cases
will doubtless reach generic rank at some future time under more
intensive study than is at present practicable. Also because of the
greater convenience in handling populous groups. In the case of
species and varieties, I have preferred inclusiveness to lumping in all
cases where doubt existed, but I have not included names based upon
mutational color patterns except when the differences are so marked
as to be a possible source of misunderstanding to the inexperienced
student. In many groups these differences are due to food, or pe-