Fig. 203.—Streptaxis Perroteti Pfr., Nilghiri Hills: A, adult; A´, young form.
The land operculate fauna of India is singularly rich and varied. About 25 genera, and at least 190 species, occur. Here we find the metropolis of Cyclophorus among the larger forms, and of Diplommatina and Alycaeus among the smaller. A large proportion of the operculate genera are quite peculiar to the extreme south of India and Ceylon. The appearance of a few species of the European genus Pomatias is very remarkable.
The carnivorous genera are poorly represented. A few Ennea occur, while Streptaxis is practically confined to the extreme south and north-east.
Land and Fresh-water Mollusca of India proper
| Streptaxis | 9 |
| Ennea | 8 |
| Helicarion | 15 |
| Girasia | 14 |
| Austenia | 11 |
| Ibycus | 1 |
| Africarion | 2 |
| Durgella | 4 |
| Ariophanta | 15 |
| Xesta | 8 |
| Macrochlamys | 78 |
| Microcystis | 7 |
| Sitala | 20 |
| Kaliella | 35 |
| Hemiplecta | 15 |
| Sesara | 3 |
| Trochomorpha | 5 |
| Trochomorphoides | 1 |
| Parmacella (?) | 1 |
| Tebennophorus | 1 |
| Anadenus | 4 |
| Plectopylis | 11 |
| Plectotropis | 3 |
| Trachia | 12 |
| Thysanota | 1 |
| Camaena | 1 |
| Amphidromus | 2 |
| Boysia | 1 |
| Petraeus | 14 |
| Cerastus | 6 |
| Rachis | 5 |
| Cylindrus | 1 |
| Pupa | 15 |
| Hapalus | 4 |
| Clausilia | 10 |
| Subulina | 2 |
| Opeas | 6 |
| Glessula | 49 |
| Geostilbia | 3 |
| Succinea | 11 |
| Lithotis | 2 |
| Vaginula | 1 |
| Camptonyx | 1 |
| Coelostele | 1 |
| Carychium | 3 |
| Ancylus | 1 |
| Limnaea | 7 |
| Camptoceras | 3 |
| Planorbis | 10 |
| Ampullarina | 1 |
| Melania | 17 |
| Mainwaringia | 1 |
| Paludomus | 10 |
| Stomatodon | 1 |
| Larina | 1 |
| Cremnoconchus | 3 |
| Fairbankia | 2 |
| Tricula | 1 |
| Bithynia | 9 |
| Fossarulus | 1 |
| Stenothyra | 3 |
| Vivipara | 4 |
| Valvata | 1 |
| Ampullaria | 4 |
| Assiminea | 9 |
| Acmella | 2 |
| Pomatias | 4 |
| Diplommatina | 63 |
| Pupina | 1 |
| Streptaulus | 1 |
| Coptochilus | 3 |
| Alycaeus | 49 |
| Lagochilus | 1 |
| Cyclophorus | 12 |
| Scalaina | 1 |
| Micraulax | 2 |
| Jerdonia | 10 |
| Spiraculum | 4 |
| Otopoma | 1 |
| Cyclotopsis | 2 |
| Georissa | 1 |
| Modiola | 1 |
| Scaphula | 1 |
| Unio | 40 |
| Solenaia | 1 |
| Cyrena | 13 |
| Sphaerium | 1 |
| Pisidium | 5 |
| Velorita | 2 |
| Tanysiphon | 1 |
| Novaculina | 1 |
| Nausitora | 1 |
The Cingalese district, which almost approaches the character of a distinct province, presents several remarkable points of dissimilarity from the rest of India. It consists of the island of Ceylon, and of a portion of S. India whose exact limits have yet to be defined. It appears, however, that the Western or Malabar coast, with the hills parallel to it, is more akin to Ceylon than the Eastern or Coromandel coast. The Travancore, Malabar, and S. Canara districts, with the Palnai, Anamalai, and Nilghiri Hills, are markedly Cingalese, while there seems to be no distinct evidence of similar relationship on the part of the Madras or even the Cuddalore district.
Among the principal features of the Cingalese district is the occurrence of three peculiar genera of Helix, one (Acavus) large and finely coloured, another (Corilla) smaller, with a singularly toothed aperture. While the Corilla group shows relations with Plectopylis and other Burmese and Siamese sub-genera Acavus (Fig. [204]) is totally distinct from any other Indian form, and shows signs of close relationship, in the great size of the embryonic shell, to the Helices of Madagascar (p. 335). In Ceylon the group is entirely isolated, and its occurrence, besides decisively separating that island from India, Burmah, and Siam, forms a most interesting problem in the history of distribution. Eurystoma, with a single species (E. vittata Müll.), is also peculiar.
As usual when Helix gains ascendancy, the Naninidae retrogress. Durgella, Austenia, and Girasia are absent altogether, while Macrochlamys, Sitala, Kaliella, etc., are present in greatly diminished numbers. The sub-genus Beddomea is peculiar, a form directly related to Amphidromus (Siam and Malacca). The fresh-water operculate Philopotamis is peculiar, but for one species found in Sumatra; while Tanalia is quite peculiar. But the forms which, next to the Helices, most emphasise the separation of the Cingalese district are the land operculates. There are eleven genera or sub-genera of land operculates which do not occur in the rest of India proper. Two (Aulopoma and Cataulus) are quite peculiar, while the other nine are represented in Burmah, Siam, and the Malay islands, but not in India. On the other hand, Diplommatina and Alycaeus, so profusely abundant in India, have not yet been discovered in Ceylon. Among the slugs, Tennentia is a peculiar genus, whose nearest relation occurs in the Seychelles.
