SIAM AND CAMBODIA 



307 



known. The tubed operculates attain their maximum, and 

 Cyclophorus is even more abundant than in India. Fiesh-water 

 bivalves abound. Dlpsas 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 Hydrohia type {^Pachy- 

 drohia^ Jullienia^ Chlorostraeia) are peculiar. 



Land and Fresh-water Mollusca of the Siamese Province 



Streptaxis . 



. 20 



Chloritis . . 



8 



Faunus . . 



1 



Leptopoma . 



10 



Ennea . . 



. 3 



Dorcasia . . 



1 



Bithynia . . 



9 



Lagochilus . 



6 



Helicarion 



. 7 



Camaena . . 



5 



Wattebledia . 



1 



Pupina . . 



8 



Microcystis 



. 3 



Hadra . . . 



5 



Stenothyra . 



4 



Hybocystis . 



3 



Sesara (?) . . 



. 1 



Obbina . . 



1 



Hydrobia . . 



1 



Alycaeus . . 



6 



Medyla 



. 1 



Amphidromus 



33 



Pachydrobia . 



9 



Cataulus (?) . 



1 



Xesta . . 



. 4 



Bocourtia . . 



2 



JuUienia . . 



6 



Diplommatina 2 



Macrochlamys 



5 . 6 



Buliminus. . 



4 



T<a,cunopsis . 



6 



Helicina . . 



4 



Kaliella . 



. 5 



Hypselostoma 



2 



Chlorostraeia . 



4 



Georissa . . 



2 



Hyalinia (?) 



. 1 



Tonkinia . . 



1 



Vivipara . . 



39 



Modiola (f . w 



)2 



Hemiplecta 



. 14 



Clausilia . . 



15 



Valvata . . 



1 



Dreissensia . 



3 



Rhysota . 



. . 2 



Opeas . . . 



7 



Ampullaria . 



15 



Anodonta 



17 



Trochomorphj 



1 . 6 



Spiraxis (?) . 



2 



Assiminea . . 



7 



Mycetopus . 



1 



Trochomorph 



Dides 3 



Subulina . . 



1 



Procyclotus . 



6 



Pseudodon . 



18 



Plectopylis 



. 5 



Succinea . . 



4 



Dasytherium . 



2 



Dipsas . . 



4 



Stegodera . 



. 2 



Vaginula . . 



7 



Opisthoporus . 



5 



Unio . . . 



64 



Plectotropis 



. 12 



Limnaea . . 



7 



Rhiostoma . 



7 



Arconaia . . 



1 



Trachia . 



. 3 



Planorbis . . 



6 



Myxostoma . 



1 



Cyrena . . 



6 



Fruticicola 



. 2 



Canidia . . 



13 



Pterocyclus . 



7 



Batissa . . 



1 



Acusta . . 



. . 2 



7I/»- 7 



Melania . . 



T-» 



39 

 1 



Cyclophorus . 

 _ ji - . j^i, _ 



28 



Corbicula 



35 



((?) The Malay Province includes the peninsula of Malacca 

 south of Tenasserim, and the series of islands beginning with 

 Sumatra and stretching eastward up to the Ke Is., besides 

 Borneo and Celebes. The Philippines form a separate province. 



The Malay province is singularly poor in representative 

 forms, whether we regard it as a whole or consider the islands 

 separately. Not a single genus, with the exception of Rhodina 

 (Malacca), appears to be peculiar. The contrast with the West 

 Indies is in this respect very striking. Java, for instance, 

 which is well explored, and almost exactly eleven times the size 

 of Jamaica, has about 100 species of land Mollusca, while 

 Jamaica has about 460. 



