I92I.] B. Prashad : Sumatran Molluscs. 487 



var. infracostata (Mousson). 



1849. Melaiiia infracostata. .Mousson, jl/o//. Java.x>'p. 65, 66, pi. .\. tig. 



187.).. Helania infracoitata, Brot. op. cit., pp.98, 99, pi. xii, fig. 3. 

 1885. Melania (A/elanoidei) variabilis var. in/rncostata, Nevill, op. cit., 



2;t. 



I agree with Nevill in considering this as onlj' a variety of 

 A. variahile. The shell is similar to that of the var. sumatrensis, 

 but is distinguished by the ribs being obsolete on the last whorl. 

 A few spiral striae are, however, to be distinguished below the 

 suture in some specimens, and these often decu.ssate as in 

 Mousson's figure. The ribs are more distinct in the 3'oung than in 

 fully-grown adults. 



I do not think that fig. 3a (pi. xii) of Brot's represents this 

 form. His figure 3 is not very good, but resembles some of the 

 specimens in the Sumatran collection. 



The following are the measurements (in millimetres) of some 

 specimens from two localities :- 



This form, like the var. sumatrensis, is a true stream form. 

 Large number of specimens of it were collected from the streams 

 vSoengei Deli (Medan) and Soengei Kalau (near Bohorok). 



var. binodulifera (Nevill). 



1885. Melania (Melanoides) variabilis subsp. episcopalis var. binoduli- 

 fera, Nevill, op. cit., p. 259. 



Nevill has discussed the mistakes committed by both Brot 

 and Hanley and Theobald (Conch. Indica) in the identification of 

 the form c'piscopalis, Lea. He was, I think, justified in giving a 

 new name to the variety with a double row of nodules in the 

 region corresponding to the ribs on the whorls in A. variabile and 

 var. sumatrensis. His specimens of the variety were collected in 

 \'arious places in Assam in the north-east of India. 



The Sumatran specimens 1 assign to this form all resemble 

 the Indian specimens. They are dull yellowish-brown in colour 

 with a few darker vertical bands. They are rather smaller than 

 those of the var. sumatrensis and have two distinct rows of small 

 nodules on the last 2^-3 whorls. On the upper whorls the 

 nodules are more or less obsolete. In younger shells, however, the 

 nodules are present on the upper whorls also. 



In the Sumatran collecJon the variety is represented by 

 specimens of all ages from the Soengei Deli (Medan), from Deli 

 (without precise habitat) and from the Soengei Kalau (a streamlet 

 near Bohorok). 



