irSITANIAX REGION. 95 



4 CydostomidiB. Of these, 60 are peculiar, 12 are common to 

 Southern Europe, and 4 to the West Indies ? 1 to Morocco, 1 to 

 Algeria (also European), and 1 to Egj'pt. The fresh-water 

 shells are Physa 2, Ancylus 1. 



Helix usfidata and McAndrei are peculiar to the rocky islets 

 known as the " Salvages," north of the Canaries. 



The absence of Western African land-shells, and the presence 

 of West Indian species may be explained by the currents which 

 come from the Antilles, as shown on the map.* Some of the 

 European species may have been introduced {e.g., Helix ladea, 

 pisaiia, cellaria) ; but the presence of 20 Lusitanian species, in a 

 total of 80, is too remarkable to be accidental. 



The Cape de Verde Islands, although much farther to the south, 

 are also much farther from the continent, being 320 miles west 

 of Cape de Yerde ; the mean temperature is 65° — 10°, and the 

 vegetation, as Dr. Christian Smith remarked, is more like that 

 of the Mediterranean coast than West Africa. Of the 12 land- 

 shells, two are common to the Canaries and Azores. 



Lusitanian Species of Wide Distribution. 



Helix amanda, Sicily — Palma. 



„ planata, Morocco — Canaries. 



„ lenticula, S. Europe — Madeira — Canaries. 



„ rozeti, Sicily, Morea — Algeria — C. de Yerde — Canaries, 



„ lanuginosa, Majorca— Algeria— Palma. 



,j simulata, SjTia — Egypt — Lancerotte. 



„ Michaudi, summit of Porto Santo — Teneriffe ? 



„ cyclodon, Azores — Canaries— C. de Verdes. 



„ advena, (= erubescens Lowe), Madeira — Azores— St. Vincent. 



„ plicaria and planorbella, Canaries - Porto Eico ? 

 Bulimus subdiaphanus. Canaries — Azores — C. de Verdes. 

 „ bceticatus and badiosus, Canaries— St. Thomas ? 



Ascension. — This barren volcanic island, in the midst of the 

 Atlantic Ocean, is not known to possess any terrestrial Pulmoni- 

 fera beside a slug, the Limax Ascensionis. Mr. Benson thinks 

 that some Helicidce might possibly be found on the Green 

 Mountain, 2,840 feet high, where the garrison have their gar- 

 dens. Mr. Darwin remarks ' ' we may feel sure that at some 

 former epoch, the climate and productions of Ascension were 

 very different from what they now are." 



St. Helena (No. 28 of Map). 

 The island of St. Helena is 800 miles S.E. of Ascension, and 

 1200 from the nearest African coast of Benguela. It is entirely 



* Long before the discovery of America it was observed that the westerly galea 

 washed ashore stems of bamboos, trunks of pines, and even living men in canoes. — 

 Humboldt, ii. p. 462. 



