56o 



Records of the Indian Museum. 



[Vol. XXII, 



Acrostoma variabilis (Benson). 

 (Plate VI, figs. 3—6.) 



Melania variabilis, Bt-nson, joiirn As. Soc. Bengal \ , p. 746. 

 Melayioides spiiiata, God\vin-.\u.stPn. Proc. Zool. Soc. London, 



p 514, pi. XXX, fig's. I, la. 

 Melania variabilis, episcopalis, spinata, Kanley and Theobald, 



Condi, /n(i.,p\. Ixxii, fig. 7. pi. Ixxv. figs. s~7' ?'• '^"i^' fi,?''- '• ^' 



6. 

 Melania variabilis, spinata, Nevill, Hand Li>t Moll. hid. Mas. 



pp. 251-261. 



This justly named species is represented in the Manipur Val- 

 ley by three varieties which link together several forms that have 

 sometimes been regarded as distinct species. The varieties, how- 

 ever, are by no means constant, though even quite young shells 

 can usually be distinguished, for many intermediate individuals 

 occur. The three Manipuri forms may be called laevis, var. nov. , 



1836. 

 1872. 



1876. 



1885. 



Fig. 9. — "^adular teeth of Melaniidae. 

 .■\. Acrostoma variabile. B. Pabidoiniis pnsfiilosa. 



semilaevigata, Nevill and suhspinata, var. nov. I will describe each 

 separately. Here I figuie a living specimen of the var. subspinata, 

 nov., from Dimapur, to show the form of the animal. 



Var. laevis, nov. : pi. vi, figs. 3, 4. Under the name semilae- 

 vigata Nevill included two forms which seem to me to be distinct 

 varieties. In one of them, for which I propose the name laevis, 

 the shell is often almost as smooth as that of Acrostoma hugeli, 

 the longitudinal ribs being completely obsolete, while in other 

 shells I assign to the same variety they are only obsolescent and 

 may even be produced into a small tubercle at the upper extre- 

 mity. This may occur either on both the two last whorls or on 

 the penultimate whorl only. The longitudinal sculpture in the 

 smoothest shells consists merely of coarse striae, while the spiral 

 sculpture is represented by ill-defined smooth ridges. The most 

 highly sculptured shells of this variety approach the var. pseiido- 

 spinosa, Nevill. 



Var. semilaevigata, Nevill: ]^\. vi, fig. 5. In Nevill's type^ 



