2 Dr. H. A. Pilsbry on 
questions of distribution and classification, to give a list of 
the species described since the beginning of the year 1900, 
and to record the somewhat extensive synonymy created 
during that period. 
The work has already reached a point where conclusions of 
general interest are appearing. The Palearctic element in 
the Japanese mollusk-fauna is inconsiderable, but the Oriental 
element has obviously reached the islands by two routes— 
a northern, vid Sachalin Island, bringing in mainland forms 
of the Amur valley and northward, and a southern, w@ the 
Loochoo chain and Formosa, and probably from Corea also, 
though until that peninsula is better known we cannot state _ 
this with confidence. Thus, to give one instance, the 
Japanese group of species commonly referred to the Helicid 
subgenus Acuséa is in reality of dual origin: the species of 
Hondo and Kiushiu(&. Steboldiana, Pfr., HE. plicosa, Martens*) 
are related through Hulota despecta of the Loochoo group to 
E. assimilis, H. Ad., of Formosa, and to species of Central 
China. ulota leta, Gld., of Hokkaido (Yesso) Island, on 
the other hand, is allied to species of Northern China and the 
Amur valley, and really belongs to the subgenus Mastig- 
eulota. A similarly dual origin can be traced in various 
other genera. 
The great number of localities explored by Mr. Hirase’s 
collectors permits us now to plot the ranges of many species 
before known from one locality or from but few places. As 
the work goes on this will enable us to formulate the lines of 
migration and the faunal zones or areas of specific and sub- 
specific differentiation. It is already clear that the islands 
composing Japan are strikingly unlike most island groups in 
this—that the several islands, as such, are younger than the 
species of snails living upon them, whereas in most island 
groups areas of specific and varietal differentiation coincide 
with the geographic limits of the several islands. In other 
words, the existing species of Japanese snails were in great 
part differentiated and acquired their present distribution 
before the islands were separated +. Present knowledge 
indicates that continuous land extended from the middle 
Loochoo group to Hokkaido, The Loochoos were first 
isolated by subsidence; then Hokkaido was cut off. Hondo, 
%* HI. plicosa seems to be merely a synonym of despecta, Gray, which 
occurs in the southern provinces of Kiushiu, as well as in the Loochoo 
slands. 
+ The evidence, so far as supplied by Helices of the Huhadra and 
Ganesella groups is concerned, has been elaborated in a still unpublished 
paper by Mr. Addison Gulick and myself. 
