96 MANUAL OF THE MOLLUSCA. 



volcanic. The indigenous plants are all peculiar, and not more 

 related to tliose of Western Africa than to Brazil. * The land 

 shells are also peculiar ; 13 species have been described, viz. * — 

 Helix, ^ sp, Bulimus 5, Achat ina 2, Pupa 1, Succinea {Ilelisiga) 

 2. As many more have been met with only in the condition of 

 dead shells, rarely retaining their colour and translucencyi 

 They are found beneath the surface-soil in the sides of ravines 

 worn by the heavy rains, at a height of 1,200 to 1,700 feet. 

 *' Their extinction has probably been caused by the entire de- • 

 struction of the woods, and the consequent loss of food and 

 shelter, which occurred during the early part of last century." 

 (Darwin's Journal, p. 488.) A living Bulimus, related to the 

 extinct B. Blofieldi, is found feeding on the cabbage-trees, only 

 on the highest points of the island. 



Extinct Land-shells of St. Helena, f 



Bulimus auris vulpinus. Bulimus relegatus. 



„ Darwini. Helix bilamellata. 



„ Blofieldi. „ polyodon. 



„ Sealei. „ spurca. 



„ subplicatus. „ biplicata. 



„ terebellum. „ Alexandii. 



„ fossilis. Succinea Bensoni. 



The large Bulimus, (fig. 123, p. 291), has no living analogue in 

 Africa, but is a member of a group characteristic of tropical 

 America (to which the names Plecochilus, Pachyotis and Caprella 

 have been given), including B. signatus, B. hilahiatus, B. goni- 

 ostomus, and especially B. sulcatus (Chilonopsis, Fischer) of St. 

 lago.J The four next species belong to the same type, but are 

 smaller and slenderer. ' ' The marine moUusks of the coast of 

 St. Helena would lead us to infer the very ancient isolation of 

 that island, whilst at the same time a pre-existing closer 

 geographical relationship between the African and the American 



« " It might perhaps have been expected that the examination of the vicinity of the 

 Congo would have thrown some light on the origin, if I may so express myself, of the 

 Flora of St. Helena. This, however, has not proved to be the case ; for neitlier has a 

 single indigenous species, nor have any of the principal genera characterising the 

 vegetation of that island, been found either on the banks of the Congo, or on any other 

 part of this coast of Africa." — R. Brown, Appendix to Captain Tuckey's Narrative of 

 tHe Congo Expedition (p. 476). 1818. 



t Gr. Sowerby in Darwin's " Volcanic Islands.'' p. 73. Forbes, Joum. Geol. Soc. 

 1852, p. 197.— Benson, An. Nat. Hist. 1851, vii. 263. 



t As Dr. Pfeiffer includes this (with a sign of doubt) amongst the synonyms of 

 JB. auris-vulpinus, he must have suspected that the specimens came from St. Helena 

 and not from St. lago. The only other group of Bulimi resembling the St. Helena 

 shells occurs in the Pacific Islands : — Bulimus Caledojiicus at Mulgrave I., B, auris 

 zc'Jiiue at the Solomons, and B. sliomji in New Zealand. 



