T. Bland on the Geographical Distribution of Mollusca. 399 
found, (as I am informed by Mr. Cuming,) in the central islands 
of the Pacific. On the other hand, there are Galapageian species 
of Oniscia and Stylifer, genera common to the West Indies and 
to the Chinese and Indian seas, but not found either on the west 
coast of America, or in the central Pacific. I may here add, that 
after the comparison by Messrs. Cuming and Hinds of about 2,000 
shells from the eastern and western coasts of America, only one 
single shell was found in common, viz., the Purpura patula, 
which inhabits the West Indies, the coast of Panama, and the 
Galapagos. We have, therefore, in this quarter of the world, 
three great conchological sea-provinces, quite distinct, though 
surprisingly near each other, being separated by long north and 
south spaces either of land or of open sea.”—p. 162. 
- Professor Edward Forbes in his able paper, “On the connection 
between the distribution of the existing Fauna and Flora of the 
British Isles, and the Geological changes which have affected 
their area, especially during the epoch of the Northern Drift,” 
published in the first volume of the ‘“ Memoirs of the Geological 
Survey of Great Britain,” (London, 1846,) gives a sketch of the 
distribution of marine Mollusca on the British shores, chiefly the 
results of his own observations. Prefatory to this sketch, he 
rves,— oy 
“Our knowledge of the species aud distribution of the British 
Mollusca is very complete, and sufficient to enable us to apply it 
to the elucidation of geological problems with safety and effect. 
hen we consider the perfect state in which the testaceous spe- 
Cies are preserved, and the facility of specific identification afforded 
by their shells, this becomes of great importance. In all ques- 
tions respecting the age of sedimentary strata, the evidence af- 
forded by the fossilized remains of the Mollusks must, from its 
view of shewing its value, 
hess of our knowledge with 
give 
seriously tended to 
shells “are regarded as specifically identical, ich, ful — 
comparison, sre found fat to be so.” To these, we think, a third — 
