Fig. 233.—A, Orthalicus Deburghiae Reeve, Ecuador; B, Bulimus (Pachyotus) egregius Jay, Brazil.
The Helicidae are most abundant in the north and west, and are represented by several very striking sub-genera, some of which possess remarkably toothed apertures, and perhaps betray an ancestry common to some of the West Indian genera. Of these, Labyrinthus has 12 species in Venezuela and Colombia, 5 in Ecuador, and 3 in Peru and Bolivia; Isomeria 12 in Venezuela and Colombia, 20 in Ecuador, and 2 in Peru and Bolivia; Salaropsis is represented in these countries by 6, 3, and 7 species, and Systrophia by 4, 5, and 8 species respectively.
Clausilia—in the group Nenia—appears in some numbers along the Andes chain, the only other representative in the New World being the solitary species occurring at Porto Rico. There have been described, from Venezuela and Colombia 10 species, from Ecuador 5, and from Peru and Bolivia 12.
Another marked feature of the region is the occurrence of the Orthalicidae, in the two genera Orthalicus and Porphyrobaphe. The latter of these magnificent forms is peculiar, while the former reaches Mexico, the West Indies, and Brazil. Ecuador, which contains 23 species, seems the metropolis of the group.
Bulimus and Bulimulus, the former genus being peculiar to S. America and the adjacent islands, are largely represented, the former in the three groups Borus, Dryptus, and Orphnus. These attain their maximum in Peru, with 25 species, but Venezuela and Colombia have as many as 17. Bulimulus has been subdivided into a number of groups, e.g. Drymaeus, Mesembrinus, Thaumastus, Mormus, Scutalus, with many others,—the exact scientific limits of which are not easily discernible. It must suffice here to state that Peru seems to be the headquarters of the group with about 190 species (which probably may well be reduced), Ecuador having about 70, and Venezuela and Colombia between 80 and 90.
Fig. 234.—Rhodea gigantea Mouss., New Grenada.
Two very remarkable forms belonging to the Pupidae, Anostoma (Fig. [154], p. 248) and Tomigerus, occur in Venezuela, the metropolis. Rhodea, another very peculiar shell (Fig. [234]), whose exact family position is uncertain, is peculiar to New Grenada. The land operculates are few in number, and in Bolivia almost disappear. They belong principally to Neocyclotus (of which 11 species occur in Venezuela and Colombia) and Helicina (10 species in the same district), besides the stragglers already mentioned from West Indian sources, and a few Cyclophorus. Bourcieria is a form of Helicina peculiar to Ecuador. Ampullaria, with Ceratodes, a peculiar planorbiform sub-genus, and Hemisinus, form the bulk of the fresh-water operculates.
The Galapagos.—Thirty-four species of land Mollusca, all peculiar, are known from these islands; 25 of these are forms of Bulimulus. There are no Helicidae, one each of Hyalinia, Leptinaria, and Helicina, and two Pupa. The Bulimulus are mostly of the group Nesiotis, and in their brown colour bear some outward resemblance to the dark Achatinella of the Sandwich Is., living as they do mostly under scoriae on the ground, and not on trees. In type, however, they appear to be derived from Chili and Peru, rather than from the parts of S. America immediately contiguous. Another section (Pleuropyrgus 2 sp.) closely resembles a marine Chemnitzia. The islands are all volcanic, and are probably not the result of subsidence; thus the existing species are not to be regarded as the relics of a more widespread fauna, but as a new set of inhabitants.