274 Records of Ihc Indian Museum. [Vol. XXII, 



but these characteristics are inconstant, especially in shells of the 

 "elongate" type, which are found not uncommonly. In both 

 this and the "normal" type, however, the shell is relatively 

 broader than in the corresponding types in the forma typica, and 

 the upper surface of the whorls is more or less broadly and 

 obliquely flattened ; the dark bands, which have the typical 

 arrangement, are as a rule slightly incrassated and the aperture 

 is subangulate, at any rate to a slight degree, at its outer and 

 lower extremity. The size is usually larger than that of balteata 

 but a little smaller than that of the forma typica. 



In some respects the three eastern races {nepalensis, balteata 

 and doliaris) represent a developmental series and would seem to 

 indicate that there has been a tendency for the species to develop 

 along certain lines as it proceeds eastwards, notably in the 

 assumption of dark spiral bands of a prominent character and the 

 special development of two of these bands as keels. A similar 

 line of development can also be traced, but less completely, in the 

 Peninsular phases of the species. 



Geographical Range. — The race doliaris has its headquarters 

 in the valley of the Irrawadi, down which its range extends at any 

 rate from Bhamo to the delta. It is also found on the lower 

 Siltang and probablj' on the lower vSalween. 



Race eburnea, nov. 

 (Plate II, figs. 1-2.) 



In this race the shell is as a rule slightly narrower than in 

 the forma typica and its aperture smaller ; the body-whorl is also 

 less enlarged and does not project outwards to the same extent in 

 dorsal view. The whorls are narrow but distinctly flattened 

 outside the suture and the body-whorl sometimes shows a ten- 

 dency to become biangulate. The longitudinal striae are very 

 fine and as a rule more regular than in bengalcnsis (s.s.), and strong 

 traces of spiral sculpture can nearly always be detected with the 

 aid of a good hand-lens. The aperture of the shell is slightly 

 pyriform and the umbilicus is very narrow if not completely 

 closed. The shell-substance when fresh has an ivorj'-like appear- 

 ance. The outer surface is lightly tinged with yellowish olive and 

 the spiral bands are never very dark. Sometimes they are obsoles- 

 cent, but traces of them can usually be found at any rate on the 

 upper whorls and the alternating broad and narrow bands are 

 often quite clear. Sometimes the dark bands coalesce on the 

 body- whorl. The aperture never has a black rim. 



Elongate shells are not uncommon and individuals inter- 

 mediate between this type and the normal one occur more fre- 

 quently than in the forma typica. 



The animal in this race is pale olivaceous and has a peculiar 

 translucent appearance, but the yellow spots characteristic of all 

 races are never obsolete. 



