1921.] N. Annandale & R. B. S. Srwell: Vivipara. 267 



Part III.— SYSTEMATIC. 

 By N. Annandale. 



The smooth-shelled dark-banded Viviparae of India and Burma 

 have given difficulty to all conchologists who have discussed them 

 in a comprehensive spirit. This is because the shells are both 

 variable individually and plastic in relation to environment. Local 

 races are also liable to become differentiated, and we find a number 

 of forms that appear at first sight to be specifically distinct but 

 are actually linked together, as becomes evident where a sufficient 

 numVjer of specimens are examined, b}- innumerable intermediate 

 tj^pes. Nevill in his unfinished Catalogue of Mollusca in the Indian 

 Museum (iS77),of which the only fragment published dealt with the 

 Ampullaridae and Viviparidae, and in his later but also unfinished 

 Hand List of Mollusca in the Indian Museum (1885), included most 

 of those forms, with several others, as varieties and subvarieties 

 under the name Pahtdina bcngalensis. So far as the species found 

 in India proper are concerned, I believe that his judgment was 

 in the main just, but the forms he assigned in 1885 to cingulata 

 (from Assam) and polygramona, von Martens, I regard as specifi- 

 cally distinct. 



Under the specific name Vivipara bengalcnsis I include all the 

 Indian forms of the genus with dark-banded shells, except the 

 Viviparae oxytropides, undescribed species from Manipur and 

 Preston's Vivipara tiagaensis, the last of which I have not seen. 

 Of V. hengalensis I recognise the following forms : — 



Race hengalensis (Lamarck). Race colairensis, nov. 



Race mandiensis , Kobelt. Phase annandalci, Kobelt. 



Race nepalensis, Kobelt. Phase halophila, Kobelt. 



Race halteata (Benson). Phase incrassata, nov. 



Race doliaris (Gould). Phase pachydolicha, Annandale. 



Race eburnea, nov. 



Vivipara hengalensis (Lamarck). 



1822. Pii/tuij'na hengalensis. Lamarck, Aniiii. s. Verf. \'I (2), p. 174. 

 1920. Vivipara hengalensis, Annandale, /?ec. Iitd. Mns. XIX, p. 113. 



The shell is ovate as a whole, sharply acuminate and with a 

 relatively large subcircular or almost rhomboidal mouth, which is 

 never very oblique. The upper part of the shell is slightly conoidal 

 rather than strictly conical. There are 5I to 6| whorls, the suture 

 is narrowly impressed and the whorls are somewhat but never very 

 greatly swollen. The spire is relatively large, usually a little 

 shorter than, but occasionally longer than the body-whorl. Its 

 whorls increase in size evenly and gradually. The body-whorl is 

 slightly oblique and always considerably broader than high, as seen 

 in dorsal view. In this view it expands but slightly towards the 



