The _Andaman_ and _Nicobar_ Islands possess no peculiar features in their land Mollusca. They are closely related to the adjacent coasts of Lower Burmah. _Amphidromus_ (2 sp.) occurs in the Andamans alone, and _Clausilia_ (2 sp.) in the Nicobars alone, while _Hyalimax_ occurs in both groups. A remarkable _Helix_ (_codonodes_ Fér.) from the Nicobars appears to find its nearest relations in the isolated group from Busuanga and Mindoro (p. 315). Land operculates are abundant, in the Nicobars actually outnumbering the pulmonates (28 to 22). _Helicina_ and _Omphalotropis_, genera characteristic of small islands, are found on both groups. (_b_) The _Siamese Province_ includes the area occupied by the districts known as Siam, Laos, Cambodia, Cochin China, Annam, and Tonquin. Along the whole of its northern frontier, the zoological is no more than a political boundary, while on the east the mountain ranges which part Siam from Pegu and Tenasserim are not of sufficient height to offer any effective barrier to distribution. The province is accordingly qualified to a considerable extent by Indian and Chinese elements. _Streptaxis_ is, but for three _Ennea_, the sole representative of the carnivorous genera, and attains its maximum in the Old World. Partly owing to Chinese influence, the Helicidae, with 11 genera and 46 species, begin to regain their position as compared with the Naninidae (12 genera, 54 species). Of the Helicidae, _Acusta_ and _Hadra_ appear now for the first time, and, with _Plectotropis_, _Stegodera_, and _Clausilia_, form a marked Chinese element. _Amphidromus_, with 33 species, is the most characteristic land pulmonate. Several genera, whose nucleus of distribution lies among the islands farther east, appear to have penetrated as far as these coasts. Such are _Chloritis_, _Camaena_, and _Obbina_ among the Helicidae, _Trochomorpha_, and, of the operculates, _Helicina_. [Illustration: FIG. 206.--_Cyclophorus siamensis_ Sowb., Siam.] Land operculates are very richly developed. In all, there are 17 genera and 104 species known. The tubed operculates attain their maximum, and _Cyclophorus_ is even more abundant than in India. Fresh-water bivalves abound. _Dipsas_ and _Pseudodon_ are common to China, and _Unio_ and _Anodonta_ are profusely represented. A curious resemblance to S. America appears in this group, a single _Mycetopus_ occurring, the only species not Brazilian, while _Arconaia_ appears very closely to approach the _Hyria_ of the same locality. Several genera of the _Hydrobia_ type (_Pachydrobia_, _Jullienia_, _Chlorostracia_) are peculiar. _Land and Fresh-water Mollusca of the Siamese Province_