INTRODUCTORY REMARKS. XV 
affinity (in their insect-inhabitants) with Porto Santo than with the 
central mass. 
In like manner, of the 162 species which have been brought to 
light in Porto Santo, 113 have been found also in Madeira, and 51 
on the Dezertas: or (in other words), scarcely more than twice as 
many, of the Porto-Santan Coleoptera, occur in the central island 
than on the small and barren rocks of the Dezertas; which (when 
we consider that the ascertained fauna of Madeira proper is nearly six 
times larger than that of the Dezertas) shows a wonderful numerical 
proportion (as in the last case) in favour of the affinity between the 
Dezertas and Porto Santo. 
Porto Santo and the Dezertas would appear indeed to have very 
much in common with each other,—far more so than with Madeira 
proper as a whole, though not much more so than they each of them 
have with the low and barren Sao Lourenco promontory which 
stretches out to the eastward of the central mass, and which would 
seem in a marked manner to contain some of the most characteristic 
insects of the other two portions of the Group. Thus, for example, 
the Tarus suturalis and Tychius robustus, of Porto Santo and the De- 
zertas, are found apparently, in Madeira proper, only on that narrow 
neck of land; the Atlantis Schawmi is peculiar to the Sao Lourengo 
promontory and Porto Santo; whilst the Helops futilis and congre- 
gatus attain their maximum on the Dezertas, and, like many other 
species, would seem to have found their way (as it were) either into 
or out of Madeira vid this low, eastern ridge,—abounding upon it, 
and gradually becoming scarcer as we approach the mountain-mass. 
And, without attempting to solve a geological problem, upon which 
Sir Charles Lyell will probably be able in a short time to throw 
considerable light, or to add any real evidence either in favour of 
or against the existence of an ancient connective land; it does cer- 
tainly appear to me, judging simply from Coleopterous data, as if the 
insect-population had possessed wonderful facilities, at some remote 
period, of migrating to and fro (as though along a slightly elevated 
mountain-ridge) between Porto Santo and the Dezertas, and in like 
manner (along a similar medium, for it is not the alpime forms that 
we can track) between the latter rocks and the eastern extremity of 
Madeira. 
Space will not permit us to enter further into these broad specu- 
lations. A few words however, ere we conclude, on one or two 
minor (though sufficiently interesting) points. I have hitherto suc- 
ceeded in detecting only 8 species on every island of the cluster ; 
they are as follows, and may be regarded as ultra-Madeiran : Scarites 
abbreviatus, Calathus complanatus, Harpalus vividus, Ptinus albo- 
