174 REVIEW OF THE CINGALESE SPECIES OF PHILOPOTAMIS AND PALUDOMUS. 



most Paludomi, for it is a general rule that low-country species of Mollusca have a wider 

 geographical range than those which are peculiar to the hills*. 



The animal of the Hoogly form has been figured by M. Souleyet (' Voyage de la Bonite ') 

 and copied by Mr. Adams in his ' Genera of the Mollusca.' Unfortunately I omitted to 

 notice the characters of the South Indian form (P. acutus, Reeve, and type of Gmelin), 

 the only one I have myself collected, and I am unable therefore to add anything from 

 my own observations. 



DESCRIPTION OE THE PLATE. 

 PLATE XXVII. 



Fig. 1 a-e. Series of Philopotamis globulosa, Gray : a, b, from Ambegammoa ; c, d, e, from Peradinia. 

 Fig. 2 a-e. Series of Paludomus Tanjoriensis, Gmelin, sp., from the Northern Province, Ceylon. 

 Fig. 3 a-e. Series of Philopotamis nigricans, Reeve : a, b, from Huckgalle ; c, from Mr. Benson's collec- 

 tion ; d, e, from Mr. Cuming's collection. 

 Fig. 4 a-f. Series of Paludomus chilinoides, Reeve : a, from Major Skinner's collection ; b, c } from 



Peradinia, Kandy ; d, e,f, from Ballepane. 



Fig. 5 a-c. Series of Philopotamis sulcata, Reeve : a, b, from Avisavella ; c, from Hautanne, Kandy. 

 Fig. 6. Philopotamis decussata, Reeve, sp., from Mr. Cuming's collection. 

 Fig. 7- Operculum of Melania variabilis, Benson : from Birma. (Enlarged 2 diameters.) 

 Fig. 8. Operculum of M. spinulosa, Lamarck : from Kandy. (Enlarged 2 diameters.) 

 Fig. 9. Operculum of M. lirata, Benson : from Calcutta. (Enlarged 2 diameters.) 

 Fig. 10. Operculum of Philopotamis decussata, Reeve, sp.: from Mr. Cuming's collection. (Enlarged 



3 diameters.) 



Fig. 11. Operculum of PA. sulcata, Reeve, sp. : from Major Skinner. (Enlarged 3 diameters.) 

 Fig. 12 a, b. Opercula of PA. globulosa, sp. : from Ambegammoa. (Enlarged 2 diameters.) 

 Fig. 13. Operculum of Tanalia violacea, Layard, sp. : from Huckgalle. (Enlarged 3 diameters.) 

 Fig. 14. Operculum of T. aculeata, Gmelin, sp. : from Ambegammoa. (Enlarged 1 diameter.) 

 Fig. 15 a, b. Opercula of Philopotamis nigricans, Reeve, sp. : a, from Huckgalle; b, from Mr. Benson's 



collection. (Enlarged 4 and 3 diameters respectively.) 

 Fig. 16. Operculum of Paludomus regulatus, Benson: from Ava. (Enlarged 2 diameters.) 



N.B. The form being the chief object of illustration, the colouring of the shells has been omitted in 

 those few specimens which exhibit markings. The shells are all of the natural size. 



F Mr. Darwin's suggestion as to the mode of dispersion of freshwater Mollusca, plants, &c., will probably apply 

 here. The stations occupied by P. Tanjoriensis are precisely those most frequented by water-fowl. 



