CHAP. XIV.] 
THE NEOTROPICAL REGION. 
33 
reptile is a land tortoise ( Testudo nigra ) of immense size,, and also 
abundant in all the islands. Its nearest ally is the equally large 
species of the Mascarene Islands ; an unusual development due, 
in both cases, to the absence of enemies permitting these slow 
but continually growing animals to attain an immense age. It 
is believed that each island has a distinct variety or species of 
tortoise. 
Insects . — Almost the only insects known from these islands 
are some Coleoptera, chiefly collected by Mr. Darwin. They 
consist of a few peculiar species of American or wide-ranging 
genera, the most important being, a Calosoma, Pcecilus, S 'olen~ 
ophorus, and Notaphus , among, the Carabidae ; an Oryctes among 
the Lamellicornes ; two new genera of obscure Heteromera ; two 
Curculionidae of wide-spread genera ; a Longicorn of the South 
American genus Eburia ; and two small Phytophaga, — a set of 
species highly suggestive of accidental immigrations at rare and 
distant intervals. 
Land-Shells. — These consist of small and obscure species, 
forming two peculiar sub-genera of Bulimulus , a genus greatly 
developed on the whole West coast of America ; and a single 
species of Buliminus, a genus which ranges over all the world 
except America. As in the case of the birds, most of the islands 
have two or three peculiar species. 
General Conclusions. — These islands are wholly volcanic and 
surrounded by very deep sea ; and Mr. Darwin is of opinion, 
not only that the islands have never been more nearly con- 
nected with the mainland than at present, but that they have 
never been connected among themselves. They are situated 
on the Equator, in a sea where gales and storms are almost 
unknown. The main currents are from the south-west, an ex- 
tension of the Peruvian drift along the west coast of South 
America. From their great extent, and their volcanoes being 
now almost extinct, we may assume that they are of consider- 
able antiquity. These facts exactly harmonize with the theory, 
that they have been peopled by rare accidental immigrations 
at very remote intervals. The only peculiar genera consist of 
birds and lizards, which must therefore have been the earliest 
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