1921.] B. Prashad : Siimatran Molluscs. 485 



Littorina conica, Phil. 



1897. Littorina conica, v. Martens, op, cit., p. ig8. 

 All the specimens of this species are from a mangrove-swamp 

 at Belawan (Deli). Some of the specimens are much darker than 

 others, while two are nearly creamy in colour. In shape and 

 sculpture, however, they are all alike. 



Family Melaniidae. 

 Genus Acrostoma, Brot. 



1920. Aci-ostoina, Atinandale, Rec. Ind. Miis. XIX, pp. log, no. 



In the paper cited above Annandale has fully discussed the 

 reasons for adopting the name Acrostoma, Brot, for the species 

 which had hitherto been classed as belonging to Melaiwides, H. 

 and A. Adams {nee Olivier), Brotia, v. Martens and " Paleome- 

 lanien," P and F. Sarasin. The only species of this genus in the 

 -Sumatran collection comprises a number of forms of the common 

 Acrostoma variabile (Benson). In the Sumatran forms I can find 

 no differences of sufficient importance to consider them as belong- 

 ing to a distinct species. They show an identically similar varia- 

 tion as regards shape and shell-sculpture as the Indian forms, and 

 many of them seem to be quite identical. I have, therefore, 

 after a careful comparison of the large series of Sumatran shells 

 with the very large collections of Indian specimens in the Indian 

 Museum, Calcutta, decided to consider them as varieties of A. 

 variabile, even though none of them are identical with the typical 

 form. 



Acrostoma variabile (Benson). 



1836. Melania variabilis, Benson, Jourii. As. Soc. Bengal, \' . pp. 746, 



1874. Melania variabilis. Brot, Melanidae in Mart, and Clieinn. 



Conch.-Cab.. pp. 85-87, pi. x, figs. ^a-d. 

 1915. Tiara (Melanoides) variabilis, Preston, Faun. Brit. Ind. 



Freshw.-Moll ., p. 23. 



This species was originally described from the Goomty River, 

 Jaunpur in the United Provinces of India, and was later found 

 by Benson in Tolly's Nullah near Calcutta. It has since been 

 found to be widely distributed, and is, as its name indicates, a 

 very variable species both as regards the shape and sculpture of 

 the shell. The Indo-Burmese forms of this species are in need of 

 a thorough revision. 



None of the Sumatran specimens belong to the tj'pical form 

 but the five varieties considered further on are represented. 

 There are besides a few specimens from some localities, which it is 

 not possible to assign to their exact varietal rank, owing to their 

 imperfect condition and to the fact that the sculpture is quite 

 eroded. 



