GALAPAGOS MOLLUSKS 
307 
couple are probably common to the islands and the main¬ 
land. All the others are restricted and quite peculiar to the 
Galapagos archipelago.* 
The genus Bulimulus, to which most of the Galapagos snails 
belong, comprises mostly species with ovate large heavy shells, 
which would seem to be peculiarly unfit for accidental trans¬ 
port by marine currents, though many live almost habitually 
on shrubs. As defined by Dr. Pilsbry, the genus is restricted, 
as I have already indicated, to the western borders of South 
and Central America and beyond the latter as far north as 
Mexico and Lower California. Eastward it passes along the 
northern States of South America to Brazil, it extends to the 
Antilles, and from Mexico to the southern United States. 
Thus it is limited to North, South and Central America, the 
West Indies and Galapagos islands. The Melanesian genera 
Liparus and Placostylus are closely related. The range of the 
large family Bulimulidae is very similar, one group being con¬ 
fined to America, the other to the opposite side of the Pacific, 
from Tasmania in the south through Australia to China north¬ 
ward, and eastward to the Society islands. One is almost 
tempted to invoke a Pacific continent in explanation of this 
curious discontinuous distribution. It seems as if the family 
had originated in some central Pacific area and had taken 
refuge on the nearest lands east and west on the disappear¬ 
ance of its ancient habitat. But we need not consider this 
problem at present. 
There are three groups of apparently very closely related 
Bulimuli in Chile and Peru, in the Galapagos islands and in 
Lower California. The shell in these groups certainly is very 
similar, being narrow and elongated, and possessing the same 
texture. All the same, Dr. Pilsbry f is of opinion that this 
similarity in appearance is not to be looked upon as indicating 
close relationship, but as a case of convergence produced by 
similar environments. He recognises three sections of Buli¬ 
mulus according to the sculpture of the apical whorls of the 
shell. The first of these lives in Argentina, Chile, Peru and 
Bolivia, the second in tropical America, the Galapagos islands 
* Dali, W. H., “ Insular Land-shell Faunas : Additions.” 
t Pilsbry, H. A., “Manual of Conchology,” (Pulmonata), X., p. 127. 
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