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ancient land ; yet our existing cluster of forms could not 

 have wandered far at that early period, from the Serras 

 and ridges of their birth, perhaps not so far indeed 

 (considering the limited bounds within which they are 

 now confined, and that time should in reality have 

 increased their range rather than diminished it) as they 

 have succeeded in doing at the present day. Hence 

 we may reasonably conclude, that Madeira proper is an 

 example of what we have alluded to in a preceding page, 

 namely, of the accidental retention, during a vast 

 downward movement, of a nucleus of small specific areas 

 of colonization, the colonizers of which had not extended 

 elsewhere. But I stated, that two of the above-men- 

 tioned Tarphii have occurred beyond the central mass, 

 It is in Porto Santo that they make their appearance ; 

 nevertheless, since one of them is apparently peculiar to 

 that island, it is only the T. Lowei, Woll. (an insect of a 

 different, and more active, nature than the rest) which 

 has violated that local exclusiveness which would seem to 

 be almost a generic character, as it were, of its allies. 

 That species, however, both in its manners and aspect, 

 recedes materially from the remainder. Although, like 

 them, nocturnal in its habits, it is able to run with con- 

 siderable velocity ; and, instead of attaching itself to the 

 blocks of putrefying wood, which both fall and decay in 

 situ on those elevated tracts, it hides within the -bunches 

 of Evernia scopulorum and prunastri which clothe the 

 trunks of living trees, and fill up the crevices of the 

 weather-beaten peaks. Hence, when contrasted with 



