CAPE REGIOX. 



97 



continents than no^^ maintains is dimly indicated. Tlie infor- 

 mation wc have obtained respecting the extinct and existing 

 terrestrial molluslsa would seem to point in tlio same direction, 

 and assuredly to indicate a closer geographical alliance between 

 Bt. Helena and the east coast of S. America than now holds." 

 (Forbes.) 



Tristan (TAcunha (No. 29 of Map). 



Two peculiar species of Balea (Tristensis and ventricosus) are 

 found on this remote and lofty island, which attains an eleva- 

 tion of 8,236 feet. 



3. Africak- Region. 



Tropical western Africa, with its hot swampy coasts and river 

 valleys is the region of the great Achatince and Achatina-like 

 Bidimi, the largest of all living land-snails. In 1863 the 

 numbers kno^-n were — Vitrina 4 sp., Streptaxis 7, Helix 30, 

 Pupa 0, Biilimus 50, Acliatina o-i, Succinea 3, and Perideris 18. 

 Sfrcptaxis Bediiziana inhabits the Guinea Islands. Helix Folini, 

 Bidimiis numidicus smd/astigiatus, Pupa ciystaJlum smd sorghum, 

 Achat ina columna, striatella, and lotophaga are found on Princes 

 Island ; Pupa putilla on Goree Island ; Bulimus {Pseudachatina) 

 Doiunesi, Achutina iostoma and Glandina cerea at Fernando Po. 

 The reversed river-snail {Lamstes) is generally diffused in the 

 fresh waters of Africa ; several species of Potamides and Vihex 

 are found in the embouchures of the western rivers and Pedipes 

 on the sea-shore. The fresh-water bivalves of Senegal are 

 similar to those of the Nile : — ■ 



Pisidium parasiticum, Egj-pt. 

 Cyrenoides Dupouti, Senegal. 

 CorLicula, 4 sp. Egypt. 



Iridina nilotica „ 



„ aegyptiaca „ 



Iiidina exotica, Senegal. 



„ rubens ,, 



Pleiodon ovatus „ 



/Etlieria semilunata „ 

 Galatea radiata „ 



Nile. 



4. Cape Eegion. 



Dr. Krauss describes 41 species of land-snail from South 

 Africa, and Mr. Benson has furnished a list containing 22 

 others ; these are all peculiar, except a Succinea, which appears 

 to be only a variety of the European S. putris, and two Em'o- 

 pean Helices (H. cellaria and pulchella) probably imported to the 

 environs of the Cape. In 1863 they had raised the number to 

 about 90. There are also 3 slugs, 9 freshwater Pulmonifera, 7 

 marine Pulmonifera, 5 freshwater bivalves, and 5 univalves. 



