Dr. Kobelt has given us such an exhaustive memoir on the characteristic Mollusca of the different zoogeographical provinces of Europe, that we are particularly well informed as regards that group of Invertebrates. He tells us that the group _Torquilla_ of the genus _Pupa_--which is a small chrysalis-like snail--is especially characteristic of the Pyrenees, Spain, and Portugal. In a certain measure they replace there the _Clausiliæ_ which, as we have seen in the last chapter, have come from the east and are almost entirely absent in the south-west of Europe. Of about seventy species of _Torquilla_, the larger number are confined to this district, and some, which like _Pupa_ (_Torquilla_) _granum_, range eastward, have travelled along the old Mediterranean highway, _viâ_ Algiers, Sicily and Greece, to Asia Minor. They are still found along the whole of this route. Similarly, we are told by the same author, that _Gonostoma_--a group of the large genus _Helix_--has a number of species in the same south-western district, while only one, viz., _Helix obvoluta_, occurs in England and Germany, and two in the Alps. Southward we again find many representatives crossing over to North Africa, among which _Helix lenticula_ has a similar range to _Pupa granum_, which I have just referred to. The Alpine sub-genus _Campylaea_ is quite absent in the Lusitanian district. Among our own British testaceous Land Mollusca, several _Helices_, viz., _Helix pisana_, _ericetorum_, _virgata_, _acuta_, _fusca_, _rotundata_, _aculeata_, and probably many others, have come to us from the south-west. The species of _Hyalinia_ are undoubtedly of very remote origin, and it would be futile at the present state of our knowledge to speculate as to their home. Some of our species may possibly be of British origin. _Balea perversa_ is probably a south-western species, and certainly _Pupa anglica_, which is quite confined to Western Europe. [Illustration: Fig. 18.--The Spotted Slug (_Geomalacus maculosus_).]