Representatives of two remarkable groups of Helix (Camaena and Phoenicobius) occur along the Palawan ridge and in Mindoro. The Phoenicobius find their nearest allies in the curious small group known as Obba, from N. Celebes, the Camaena possibly in a type of Helix (Hadra) occurring in New Guinea and N.E. Australia. The only other Helix from the whole of the E. Indies which bears any resemblance to the Phoenicobius group is H. codonodes Pfr., which is peculiar to the Nicobars. A few forms assigned to Camaena also occur in Further India and Siam. It would appear possible, therefore, that these two isolated groups are a sort of survival of a fauna which perhaps had once a much more extended range.
(2) The Chinese Sub-region.—The Chinese Sub-region includes the whole of China from its southern frontier up to and including the basin of the Blue or Yang-tse River, together with the coast district, including Corea, perhaps as far north as Vladivostok, and the outlying islands of Hainan, Formosa, the Loo-Choo and Bonin groups, and Japan to the north of Niphon. It may be divided into two provinces, the Chinese and the Japanese.
(a) The fauna of the Chinese province proper bears, in many respects, strong marks of relationship to that of India and Siam. Thus Streptaxis, Helicarion, Macrochlamys, Kaliella, Sitala, Ariophanta, Rhysota, Hemiplecta, Diplommatina, Opisthoporus, Pterocyclus, Lagochilus, and Alycaeus all occur, especially in Southern China. The two points in which the sub-region bears special marks of individuality are Helix and Clausilia. The sub-genera of Helix which have their metropolis in China are Satsuma, Cathaica, Aegista, Acusta, Euhadra, Plectotropis, and Plectopylis. Sinistral forms (compare Fig. [213]) are rather prevalent. In several cases—e.g. Trichia, Gonostoma, Fruticicola—there is a reappearance of forms which appear to belong to well-known European sub-genera. Clausilia here attains a kind of second centre of distribution, and is represented by its finest forms, which belong to several peculiar sub-genera. The carnivorous Mollusca are not abundant, and are represented by Rathouisia (a peculiar genus of naked slug), Ennea, and Streptaxis. In the western provinces Buliminus is abundant in several sub-genera, one of which appears to be the European Napaeus.
Fig. 213.—Helix (Camaena) cicatricosa Müll., China.
There is little which is striking in the operculates, which are most abundant in the south, and appear to be mainly derived from Indian and Siamese sources. The occurrence of Helicina (3 sp.), Omphalotropis (1), Leptopoma (2), and Realia (2), is evidence of some influence from the far East. Heudeia is a very remarkable and quite peculiar form of Helicina with internal plicae, perhaps akin to the Central American Ceres.
Fresh-water genera are exceedingly abundant, especially Melania, Unio, and Anodonta. The occurrence of Mycetopus (a South-American genus) is remarkable. There are several peculiar forms of fresh-water operculates, whose exact position is hardly yet assured.
Land and Fresh-water Mollusca of the Chinese Province
| Rathouisia | 1 |
| Streptaxis | 7 |
| Ennea | 12 |
| Parmarion | 2 |
| Helicarion | 15 |
| Euplecta | 3 |
| Macrochlamys | 19 |
| Microcystina | 2 |
| Microcystis | 7 |
| Kaliella | 16 |
| Sitala | 8 |
| Ariophanta | 1 |
| Rhysota | 5 |
| Hemiplecta | 1 |
| Trochomorpha | 2 |
| Limax | 1 |
| Philomycus | 1 |
| Patula | 2 |
| Gonostoma | 4 |
| Metodontia | 2 |
| Vallonia | 1 |
| Plectotropis | 9 |
| Fruticicola | 11 |
| Satsuma | 14 |
| Trichia | 10 |
| Cathaica | 22 |
| Aegista | 10 |
| Armandia | 3 |
| Acusta | 15 |
| Obbina | 1 |
| Camaena | 5 |
| Euhadra | 14 |
| Plectopylis | 19 |
| Stegodera | 6 |
| Chloritis | 1 |
| Hel. Inc. sed. | 39 |
| Buliminus | 21 |
| Buliminopsis | 3 |
| Buliminidius | 3 |
| Napaeus | 14 |
| Rachis (?) | 4 |
| Pupa | 10 |
| Clausilia | 102 |
| Opeas | 12 |
| Euspiraxis | 1 |
| Subulina | 5 |
| Stenogyra (?) | 12 |
| Succinea | 8 |
| Vaginula | 7 |
| Limnaea | 2 |
| Planorbis | 6 |
| Melania | 44 |
| Paludomus | 3 |
| Bithynia | 12 |
| Lithoglyphus | 3 |
| Melantho (?) | 1 |
| Pachydrobia | 1 |
| Prososthenia | 2 |
| Stenothyra | 2 |
| Hydrobia | 2 |
| Mecongia | 1 |
| Oncomelania | 9 |
| Margaracya | 1 |
| Rivularia | 4 |
| Delavaya | 1 |
| Fenouillia | 1 |
| Vivipara | 34 |
| Diplommatina | 20 |
| Pupina | 6 |
| Alycaeus | 23 |
| Leptopoma | 2 |
| Lagochilus | 10 |
| Cyclophorus | 18 |
| Coelopoma | 1 |
| Pterocyclus | 3 |
| Opisthoporus | 4 |
| Cyclotus | 10 |
| Scabrina | 4 |
| Ptychopoma | 12 |
| Omphalotropis | 1 |
| Realia | 2 |
| Pseudopomatias | 1 |
| Helicina | 3 |
| Georissa | 4 |
| Heudeia | 1 |
| Cyclas | 1 |
| Corbicula | 50 |
| Unio | 53 |
| Monocondylaea | 1 |
| Anodonta | 55 |
| Mycetopus | 12 |
| Pseudodon | 1 |
| Dipsas | 4 |
The island of Hainan, in the extreme south of the sub-region, has 40 species of Mollusca, 22 of which are peculiar, but there is no peculiar genus.