252 Records of the Indian Museum. [Vol. XVI, 



that the only known species is a depauperated form modified in 

 accordance with an amphibious life partly spent in water of con- 

 siderable salinity. 



The sub-genus may be redescribed as follows, using Nevill's 

 terms to a large extent : — Melaniidae with imperforate, conically 

 produced shell ; its spire turretedly acuminate ; shell-substance 

 thick and almost porcellaneous, but becoming much thinner in the 

 lower part of the body- whorl ; columella strongly arched, not 

 greatly incrassate, outer lip sharp ; external surface decorated 

 with deep-cut spiral striae ; a thin epidermis present, bearing 

 minute scattered hairs or chaetae. Operculum horny, extremely 

 thin, paucispiral, with the nucleus eccentric. 



Animal differing from that of the groups Plotia, Striatella , 

 Melanoides, and Tarehia in the following characters : — Foot pointed 

 and produced into a short filamentous process behind ; a distinct 

 mid-dorsal groove on posterior part of the foot extending on to 

 the terminal process. Radula (fig. ^a) like that of Melania, but 

 without a distinct cusp to the median tooth and with marginal 

 teeth of peculiar form (see figure 56). 



Type: Mainwaringia paludomidea,Nevi\\. 



Distribution. — Only known from the lower parts of the Gan- 

 getic Delta. 



Melania (Mainwaringia) paludomidea, Nevill. 

 (Plate XX. fig. 8). 



Nevill's description of the shell, which is quoted by Preston 

 on p. 37 of his volume in the " Fauna," needs no elaboration. 

 The animal has the characters noted above. Its foot is rather 

 small; the tentacles are very long, slender and tapering, with the 

 eyes situated on distinct prominences at their base externally. 

 The snout is prominent, blunt and slightly notched in front. The 

 foot and tentacles are transluscent white, suffused with black 

 pigment above; the snout is brownish. The branchial chamber 

 resembles that of Melania, but the branchial folds are exception- 

 ally deep. The osphradium is well developed and ridge-like. 



The species is not uncommon between tide-marks in the lower 

 parts of the Gangetic Delta. At low-tide it adheres tightly by 

 means of a gummy secretion to the trunks of trees, and particularly 

 to the upright aerating roots of mangroves. When placed in 

 water it emits a bubble of air and immediately becomes active. 

 It would seem, therefore, to breathe air while in a comatose condi- 

 tion at low- tide, but never to be active while doing so. 



Family NASSIDAE. 



Genus Nassa, Lamarck. 



The small species of this genus that occur in brackish water 

 on the coast of India, all of which have recently been described 

 by Preston, seem to form a very distinct little group, in which 



