underground on
earthworms, and of which genus three species, viz. _T. maugei_, _T.
haliotidea_, _T. scutulum_, are known to inhabit the British Islands, is
another Lusitanian animal. All the species are confined to Western
Europe and North Africa; they do not even reach Germany or Switzerland.

[Illustration: Fig. 19.--Map of the British Islands on which the
geographical distribution of _Geomalacus maculosus_ is indicated in
black.]

I have had occasion to mention once before an extremely interesting
genus of blind Woodlouse, viz., _Platyarthrus_. Like _Testacella_, it
lives underground, and also resembles it in its general range. Its
distribution is therefore of particular interest. It is difficult to
conceive that _Platyarthrus_, from its peculiar mode of life could have
crossed any formidable barrier, such as even a narrow straits of sea.
Its occurrence in Spain and North Africa indicates, therefore, that the
Straits of Gibraltar did not exist at the time when it undertook the
migration southward, just as the English Channel and the Irish Sea could
not have been there when it wandered to England and Ireland. The species
which occurs in the south of England has a wide range in Ireland, and
reaches in Scotland its most northern European limit of distribution.
_Platyarthrus_ is only one of the Lusitanian genera of woodlice. In
Ireland--chiefly on the west coast--we also find a brilliantly coloured
Woodlouse, which is absent from Great Britain, viz. _Metoponorthus
cingendus_. It reappears again on the Continent in the south of France.
Its range is therefore suggestive of a Lusitanian origin; and indeed,
when we examine the general distribution of the genus _Metoponorthus_,
we find that out of the forty-four known species, fully one-half are
confined to Western Europe and North Africa.

My friend and colleague, Mr. Carpenter, informs me that among the Irish
Spiders he is acquainted with, the following are to be looked upon as
Lusitanian species:--

Dysdera crocota.
Oonops pulcher.
Tegenaria hibernica.
Theridion aulicum.
Lasaeola inornata.
Agroeca celans.
do. gracilipes.
Teutana grossa.
Cnephalocotes curtus.
Porrhomma myops.

Of the _Coleoptera_, the genera _Trichis_, _Glycia_, and _Singilis_, all
belonging to the Running Beetles (_Carabidae_), are almost confined to
the Spanish peninsula.

The beetles _Rhopalomesites Tardyi_, _Eurynebria complanata_, and
_Otiorrhynchus auropunctatus_