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_.