X UPPER BURMAH AND PEGU 305 



and Aracan, while essentially a part of the Indian province, 

 contains several Siamese genera which are. not found in India 

 proper, as well as several which are at present peculiar. 

 Amongst the former category are, of Helicidae, a single repre- 

 sentative each of the genera Camaena (Siamese and Chinese) and 

 Aef/ista (Chinese). Influence of the same kind is seen in the 

 increased numbers of Plcctopylts (14 sp.) and Plectotropis (5 sp.), 

 of Clausilia (10 sp.) and Amjphidromus (5 sp.), 

 and of the large tubed operculates (11 sp. in all). 

 Sesara and Sophina among the Naninidae are strange 

 to India, while Hyalimax is common only to the 

 Anclamans, Nicobars, and Mascarene Is. Ilj/j^sclo- 

 stoma (Fig. 202, A) is a most remarkable genus of 

 the Pupidae, reminding one of Anostoma of the 

 N'ew World. It is peculiar to the peninsula, but 

 for one species in the Philippines. Among the 

 Pupinidae, we have the peculiar Eaphaulus and 

 Hyhocystis (Pig. 205), a very remarkable form, of 

 which another species occurs at Perak. Tvfo Helicinct ^m. 2Q5.—Hyho- 

 mark the most westward extension of the genus <^ystis gravida 



• 1 1 T 1 1 j:- TT Bens. Young 



on the mainland. In the extreme north 01 Upper and adult. 

 Burmah, Indian and Chinese forms intermingle. 



The Burmese district, together with the Indian and Siamese 

 provinces, is pre-eminently the home of a group of Mollusca, 

 originally of marine origin, which have permanently habituated 

 themselves to a brackish or fresh-water existence. They belong- 

 to widely different families, and even Orders. Besides Cremnocon- 

 chus mentioned above, we have, among the l)ivalves, Novaculina, 

 a Solen living in fresh water in the Ganges, Irawadi, and 

 Tenasserim estuaries ; Scaphida, an Area, one species of which 

 occurs in the Ganges hundreds of miles above the tideway (see 

 Pig. 9, p. 14); and Martesia, a Pholas from the Irawadi Delta. 

 Clea (which also occurs in Java and Sumatra) is probably an 

 estuarine Cominella; a Tectiira has earned the name fiuminalis 

 from its exclusive residence in the Irawadi R; Iravadia is 

 probably a Bissoina of similar haliits, occurring from Ceylon 

 round to Hong-Kong ; JBrotia is a Cerithium from an affluent of 

 the Eiver Salwin, and Canidia is a liassa, occurring in the 

 embouchures of rivers from India to Borneo. Nowhere else in 

 the world is there such a collection- — not exhausted by this list 



VOL. Ill X 



