1877.] On the Vitality of certain Land Mollusks. 101 
species has been quoted from Oregon, and (4) H. levis from the 
Columbia River, in both cases erroneously. The figures in Land 
and Fresh Water Shells of North America,! page 177, are too 
elevated and globose for the typical areolata, but the larger fig- 
ures faithfully represent H. Veatchit. Elevation and rotundity 
are insular characteristics in this group, and areolata is somewhat 
depressed. It is found in comparative abundance on the uplands 
around Magdalena Bay, which is on the outer or ocean shore of 
the peninsula, in latitude about 24° 40! N. 
Bulimus pallidior, which is pretty generally distributed through 
Lower California, from Cape St. Lucas northerly, has also errone- 
ously been credited to San Diego in California proper. 
It is arboreal in its habits, at least during the winter season, 
being found on copaiva trees. It has been said to inhabit South 
America, which is probably incorrect, and the locality “ San 
Juan ” mentioned in Land and Fresh Water Shells, on page 195, 
where a good figure of this species may be seen, should be San 
Juanico, which is on the east or gulf side of the peninsula, in 
latitude about 27° N. 
The great importance of accuracy in habitat will be at once 
perceived when I state that there are no less than three other lo- 
ealities on the west coast of America, north of the place cited, all 
of which are referred to in various scientific works, which have 
come under my observation as San Juan, and there are per- 
haps as many more San Juans, south of that especially quoted 
herein, on the westerly coast of America, in the Central and 
South American States. Attention is directed to the fact that 
the three species here mentioned as exhibiting extraordinary 
vitality belong to geographical areas which receive only a mini- 
mum rainfall, or which are, in simple language, nearly rainless 
regions. ; 
Within such areas vegetation is exceedingly limited even in 
favorable seasons, and the presence and growth of the annual 
plants is of course dependent upon the rainfall ; this last occurring 
infrequently makes the food supply of land mollusks and other 
phytophagous or vegetable-eating animals exceedingly precari- 
ous, ; 
; It is highly probable that a careful investigation in this direc- 
tion will lead us to the conclusion that the land mollusks which 
inhabit these arid areas have, through selection, adaptation, and 
evolution, become especially fitted for the contingencies of their 
1 Smithsonian Misc, Coll., No. 194. 
