144 
THE NAUTILUS. 
NEW PUBLICATIONS. 
Distribution of the Land and Fresh-water Mollusks of 
the West Indian Region, and their Evidence with Regard to 
Pa9t Changes of Land and Sea. By Charles Torrey Simpson (Proc. 
U. S. Nat. Mus., XVII, 1894).—After a statement of the geographic 
facts in regard to the region, and the depths of sea between and 
around the main islands, Mr. Simpson considers the means of distri¬ 
bution of the land and fresh-water mollusks from island to island, 
concluding that while some forms have been transported by drifting 
trees, etc., the main means of transport has been by means of former 
direct land connection of islands now separated. “ There appears 
to be good evidence of a general elevation of the Greater Antillean 
region, probably some time during the Eocene, after most of the im¬ 
portant groups of snails had come into existence, at which times the 
larger islands were united, and there was land connection with Cen¬ 
tral America by way of Jamaica. * * * At some time during 
this elevation, there was probably a landway from Cuba across the 
Bahama plateau to Florida, over which certain groups of Antillean 
land mollusks crossed. * * * There followed a period of general 
subsidence. During this the island of * * Jamaica was first 
isolated, then Cuba, and afterwards Haiti and Puerto Rico were 
separated. The subsidence continuing until only the summits of the 
mountains of the four Greater Antilles remained above water ; then 
followed another period of elevation which has lasted until the pres¬ 
ent time. * * The Bahamas have appeared above the surface of 
the sea, either by elevation or growth, and have been peopled by 
forms drifted from Cuba and Haiti. The lesser Antilles have been 
peopled, for the most part, from S. America.” These conclusions 
are based upon tables showing the distribution of species and genera 
on the various islands, and the later movements are supported by 
well-known geological facts. The evidence for the earlier elevation 
should be compared with Spencer’s “ Reconstruction of the Antillean 
Continent” (Bull. Geol. Soc. Amer., VI, Jan., 1895), founded upon 
a study of the supposed sunken river-valleys, and altogether support¬ 
ing Mr. Simpson’s conclusions. That the West Indian region ac¬ 
tually stood two miles above its present level, as claimed by Spencer, 
is a proposition requiring much more proof than has been offered, to 
bring it out of the realm of mere suggestion or hypothesis ; and we 
are certainly not prepared to endorse it; but the orogenic move¬ 
ments required to fulfill the conditions asked by Mr. Simpson are far 
more moderate, and, it seems to us, by all odds the most reasonable 
explanation of the facts of distribution. Mr. Simpson’s paper con¬ 
cludes with the descriptions of Sagda maxima, Neocyclotus bakeri, 
Lucidella costata and Pleurodonte boivdeniana n. spp., from Jamaica, 
the latter three from the Miocene beds at Bowden. 
