298 THE ATLANTIC ISLANDS chap. 



Helix (the sub-genera being very much the same as in the 

 Madeiran group), and 11 to Patula. There is 1 species of 

 Parmacella (which occurs in this group alone), and 6 of Vitrina^ 

 of considerable size. A remarkable slug (^Plectrophorus^ was 

 described from Teneriffe by Ferussac many years ago, but it has 

 never been rediscovered, and is probably mythical, or wrongly 

 assigned. Buliminus (^Napaeus) has as many as 28 species, all 

 but one being peculiar, and Ferussacia 7. Cyclostoma has two 

 indigenous species, which, with one Hydrocena and one Craspedo- 

 poma, make up the operculate land fauna. 



The Azores are comparatively poor in Mollusca, having only 

 52 species, nearly two-thirds of which are peculiar. Helix has 

 15 species, Patida 4, and Pupa 8. Ferussacia^ so abundant in 

 Madeira and the Canaries, is entirely absent, its place being 

 taken by Napaeus (7 sp.), which is curiously absent from 

 Madeira, but richly represented in the Canaries. There are 7 

 Vitrina^ while the land operculates consist of one each of 

 Oraspedopoma and Hydrocena. A singular slug (^Plutonia)^ with 

 an ancyliform internal shell, is said to occur. The group was 

 long believed to possess no fresh-water Mollusca, but two species 

 (one each of Pisidium and Physa^ have recently been discovered. 



The Cape Verdes, owing to the extreme dryness of their 

 climate, are poor in land Mollusca. There are 11 Helix, nearly 

 all of which belong to the group Leptaxis, which is common to 

 Madeira and the Canaries. Ferussacia is absent, Buliminus is 

 represented by a single species, and there are no land operculates. 

 Ethiopian influence, however, as might be expected from the 

 situation of the group, is seen in the occurrence of an Ennea, a 

 Melania, and an Isidora. 



It will be noticed how little countenance the moUuscan fauna 

 of these island groups gives to any theory of an Atlantis, any 

 theory which regards the islands as the remains of a western 

 continent now sunk beneath the ocean. Had ' Atlantis ' ever 

 existed, we should have expected to find a considerable proportion 

 of the Mollusca common to all the groups, and perhaps to Europe 

 as well, and there would apparently be no reason why a genus 

 which occurred in one group should not occur in all. As a fact, 

 we find the species extremely localised throughout, and genera 

 occur and fail to occur in a particular group without any 

 obvious reason. All the evidence tends to show that the islands 



