208 CANTDIA. 



the form and sculpture of the shell do not contravene such a dis- 

 position of GJea^ its fluviatile distribution being actually the 

 strongest argument for considering it a Melania. As to the 

 genus Ganideo, the differential characters are slight and of 

 specific value only, except that the margin of the aperture is 

 sinuated in front in all the species, and this may serve as a con- 

 venient means of dividing the genus GJea into two groups, one 

 of which ma^" bear the name of Ganidea as a subgenus. The 

 dirt'erences in operculum and dentition pointed out by Brot are 

 unimportant. The geographical disti'ibution of the genus com- 

 prises the Malaysian Peninsula and Archipelago. It would be 

 interesting to ascertain whether the waters inhabited are really 

 fresh, or perhaps brackish. 



For the species, I follow the monograph by Dr. A. Brot, pub- 

 lished in the "Journal de Conchyliologie," 18T6. 



C. NIGRICANS, A. Adams. PL 81, figs. 445, 44fi. 



Ejiidermis dark olive, aperture light chocolate. Length, 28 mill. 



Sarawak, Borneo. 

 G.funeata.^ A. Adams, an unfigured species from Malacca, does 

 not appear to differ specificnlly, judging from the description. 



Subgenus Canidia, A. Ad. 



C. Helena, Meder. PI. 81, figs. 441, 448. 



Yellowish olive, with two chestnut Itauds. Length, 20 mill. 



Jaoa. 

 I do not find any good characters l)y which to separate G. 

 Theminckiana , Petit (fig. 448), an immature shell. 



0. TENUicosTATA, Brot. PI. 81, fig. 449. 



Brown, without bands. Length, 21 mill. 



Pexahury, Siam. 

 Perhaps a variety of G. Ilelma. 



C. Baudontana, Maltille and Lc Mesle. PI. 81, fig. 450. 



Yellowish olive, the bands chestnut-brown. Length, 30 mill. 



Hondoru], Cambodia. 

 With a longer spire than G. Helena, and three; bands, this ma}' 

 still be only a variety of it. 



