394 7’. Bland on the Geographical Distribution of Mollusca. 
*‘ Another point of interest extensively elucidated by the col- 
lections of the Expedition is the occurrence of analogous species 
in co-ordinate regions. It is now a received fact that the animals 
and plants of the northernmost zones are, for the most part, iden- 
tical throughout the whole circuit ; and that the species gradually 
diverge from each other towards the equator, on the three conti- 
nents; and that after passing the equator towards the south, there 
is not a return to the same species, and rarely to the same genera, 
as we should expect if variation of forms depended mainly on 
difference of temperature. There is, however, a return to mol- 
lusks of a kindred character and form, and oftentimes to the same 
isothermal latitude. In the latter case we may have anal€gous 
enera. Along our northern seas, some of the most characteristic 
shells are Buccinum, Tritonium, Fusus, Terebratula, Rimula, 
Around Cape Horn are shells of the same types, so closely 
though peculiar in many important respects. But this resem- 
blance does not descend to species. In the first case, however, 
not only have we the same genera, but the species seem to repeat 
each other: so that species brought fom great distances east or 
west, are scarcely to be distinguished upon comparison.” —p. Xu. 
Dr. Gould gives, in illustration, a list of species from Oregon, 
and from the Eastern States, and observes that “mingled with 
ties as constituting very different zoological regions.” He a 
“the same comparison holds good between the shells of the Gulf 
of California and the Gulf of Mexico.” 
We would quote also the following :— 
“From a consideration of the land shells collected on the Pa- 
cific Islands, it seems possible to draw some fair inferences as to 
the relations of the lands which once occupied the area of the 
Pacific Ocean, and whose mountain peaks evidently now indicate 
or constitute, the islands with which it is now studded. : 
observation of the species, we think there are strong indications 
that some groups of islands have an intimate relation to each 
other, and belonged, at least, to the peaks of the same mountain 
ranges, before they were submerged; while the indications are 
equally strong that other groups had no territorial connection. 
—p. xiv. : 
Drawing inferences from the land shells, Dr. Gould considers 
that the Samoa and Friendly Islands are more intimately rela- 
ted to the Society Islands, though at a much greater distance, 
than to the Feejee Islands, and that the Feejees are more nearly 
allied to the islands to the westward,—such as the New Hebzrides, 
than to the Friendly Islands on the east, though so much nearer. 
