1921.] N. Annandale & K. B. S. Sewell : Vivipara. 273 



Race balteata (Benson). 

 (Plate I, fig. 8.) 



1836. Paludina heiigalcHsis. \nr. balteata, Benson, youvn. As. Soc 



Beng. pt. 2, p. 745. 

 igoy. Vivipaya {bengalensis var.) balteata. Kobclt, op. ci't., p. 4.15, pi, 



Ixxvii, figs, 11-12. 



Were all the shells of this race like the one figured by Kobelt, 

 there would be little doubt as to the propriety of regarding it as 

 r^pecifically distinct ; but his figure represents an extreme type, 

 which, though common, is by no means universal in the race. My 

 own figure (pi. I, fig. 3) represents a shell that goes almost to the 

 opposite extreme. Both types are present in several series exam- 

 ined from S5'lhet and the eastern parts of the Brahmaputra vallej'. 

 It will be noticed that Kobelt' s figure represents a small shell of 

 the " elongate " type, mine a larger one of the " normal " type. 



Most shells resemble the former. They rarely exceed 20 mm. 

 in height and are narrow in proportion. The whorls are some- 

 what contracted, the aperture ovoid and the umbilicus closed. The 

 dark bands are well developed and sometimes all of them are very 

 narrow. They are frequently thickened and prominent. Shells of 

 the '• normal " type are often larger, with a very large sub-circular 

 aperture. Their body-whorl is frequently almost biangulate, and 

 the dark l:)ands alternate in width. Intermediates between the 

 two types are not uncommon. In both types, the shell is very 

 thin and quite translucent when fresh. Specimens can often be 

 found so similar to some of those of the Burmese race doliaris 

 that they can hardly be distinguished from them. Others closely 

 resemble Peninsular shells of the phase annandalci. 



Geographical Range. — The headquarters of this race is the 

 Sylhet valley in southern Assam, but it also occurs in the eastern 

 part of the valley of the Brahmaputra. It is absent from 

 Manipur. There are specimens in the Indian Museum labelled 

 Siliguii but this is probably a mistake for Silcuri in Cachar, 

 where Benson originally obtained specimens. 



I am informed that this race is often found in flooded rice 

 fields. 



Race doliaris (Gould). 



(Plate I, fig. 9.) 



1843. Paliuiina doliafis, Gould, Pi-oc. Bost. Soc. Nat. Hist. 1, p. 144 

 1869. Paludina digona. Blanford, Proc. Zool. Soc. London., p. i,.\^. 

 1876. Paludina diguna. Hanley and Theobald, op. cit., pi. cxv, fig. 7. 



The most characteristic feature of this race is the one des- 

 cribed in Blanford' s name digona. The biangulate outhne 

 of the body-whorl is due to the presence of two spiral ridges 

 which are merely dark bands thickened, but this feature is not 

 equally developed in all individuals and in some is almost absent. 

 In typical specimens the aperture is exceptionally large and wide, 

 the columellar edge prominent, and the umbilicus rather broad ; 



