As we go down in the scale of life—among the lower vertebrates and invertebrates—we meet with a greater number of prominent members of the Lusitanian migration. The Bullfinch, Dipper, and Chough, which might be thought to be of Lusitanian origin, are, as I have shown in the last chapter, Asiatic.
The European snakes seem to be all of eastern origin, unless Tropidonotus viperinus might be claimed as a Lusitanian form. Of very great interest from a zoogeographical point of view is our only European member of the South American and African family Amphisbænidæ. This species—Blanus cinereus—is of the size and shape of an ordinary earth-worm, from which, however, it may be distinguished by its snake-like wriggling motions. It lives under stones in Spain and Portugal, North-west Africa, and Greece. It has, therefore, a somewhat similar distribution to that of many of the animals and plants referred to in the last chapter. But here we have an animal which has evidently utilised the old Mediterranean route described on p. [271], from west to east. Two other species of Blanus inhabit Asia Minor and Syria, but most of its nearest relations either live in South America or tropical Africa. In migrating to North and West Africa, its ancestors probably made use of the land-bridge which spanned the Atlantic in early Tertiary times. Another Lusitanian Lizard—belonging not to an aberrant group, but to the typical Lacertidæ—is Psammodromus hispanicus. It is rather variable in colour—generally of a brown or green—and grows to a length at about four or five inches. It occurs throughout the Spanish peninsula and also in Southern France. One of the handsomest European Lizards, which reaches almost a foot in length,—of an olive colour with greenish or mother-of-pearl reflection, and with two yellow stripes along each side of the body,—is an allied species (P. algirus). From the Spanish peninsula it passes into Southern France and North Africa. Two other species of the genus are confined to North-west Africa.
It is quite possible that the genus Pelobates is of south-western origin. Of the two known species of this genus of Toads, one is found in the Central European plain and the other on the Spanish peninsula and in France. The closely allied Pelodytes punctatus, too, is confined to this south-western district, and their nearest relations are found in Mexico. Similarly, the genus to which the Midwife Toad (Alytes obstetricans) belongs may have its original home in that part of Europe. Of the two species, one is confined to France, Switzerland, Belgium, and Western Germany, and the other, viz., Alytes cisternasii, to Spain. Discoglossus pictus—a well-known and conspicuous Toad in Southern Europe—inhabits Spain, Algiers, and Tunis, the islands of Malta, Sicily, Sardinia, and Corsica. From the general range of the family Discoglossidæ, as given in Mr. Boulenger's excellent catalogue, it appears that nowhere in the vast space between China and New Zealand has any member of the family been discovered. The peculiar genus of Salamander—Chioglossa—is quite confined to the Spanish peninsula.
The Butterflies Nemeobius lucina and Charaxes jasius may also have had their home in that south-western district. To this migration also seems to belong the genus Gonepteryx, which has so peculiar a range in the British Islands. The only British species, known as the Brimstone Butterfly (Gonepteryx rhamni), occurs in the south of England and in the south and west of Ireland. It is met with over the greater part of Europe, and its range extends into Asia Minor and Northern India, and then it reappears again in distinct varieties in Japan and the Amur district. Three other species of Gonepteryx are known from Tibet and India, and one (G. cleopatra) from Southern Europe and Northern Africa. All the remaining species inhabit the west, viz., Brazil, Mexico, and Venezuela. That the genus has migrated from America eastward to Europe appears to be more probable than a migration in the opposite direction. At any rate, that an exchange of species between the south-western portion of the Holarctic Region and the Neotropical area took place is indicated by the fact, not only that a variety of G. cleopatra has been found in Madeira, but also that the Canary Islands possess a distinct form of Gonepteryx, viz., G. cleobule.
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.
