CHAP. XII.] 
THE AZORES. 
247 
Brazilian elater appears to be the solitary example of a living 
insect brought by the Gulf Stream to these remote shores. 
The elater, having its nearest living ally in Madagascar 
( Elastrus dolosus ), cannot be held to indicate any independent 
communication between these distant islands; but is more 
probably a relic of a once more widespread type which has 
only been able to maintain itself in these localities. Mr. 
Crotch states that there are some species of beetles common to 
Madagascar and the Canary Islands, while there are several 
genera, common to Madagascar and South America, and some to 
Madagascar and Australia. The clue to these apparent anomalies 
is found in other genera being common to Madagascar, Africa, 
and South America, while others are Asiatic or Australian. 
Madagascar, in fact, has insect relations with every part of the 
globe, and the only rational explanation of such facts is, that 
they are indications of very ancient and once widespread groups, 
maintaining themselves only in a few widely separated portions 
of what was at one time or another the area of their distribution. 
Land-shells of the Azores . — Like the insects and birds, the 
land-shells of these islands have a generally European aspect, 
but with a larger proportion of peculiar species. This was to be 
expected, because the means by which molluscs are carried over 
the sea are far less numerous and varied than in the case of 
insects j 1 and we may therefore conclude that their introduction 
is a very rare event, and that a species once arrived remains for 
long periods undisturbed by new arrivals, and is therefore more 
likely to become modified by the new conditions, and then fixed 
as a distinct type. Out of the sixty-nine known species, thirty- 
seven are common to Europe or the other Atlantic islands, while 
thirty-two are peculiar, though almost all are distinctly allied to 
European types. The majority of these shells, especially the 
peculiar forms, are very small, and many of them may date 
back to beyond the glacial epoch. The eggs of these would be 
exceedingly minute, and might occasionally be carried on leaves 
or other materials during gales of exceptional violence and 
duration, while others might be conveyed with the earth that 
often sticks to the feet of birds. There are also, probably, other 
1 See Chap. V. p. 76. 
