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 them.selves 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 ;^ 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. 



