igig.] N. Annandale : Bombay Streams Fauna. 119 



Molluscs. — Two species of molluscs, both belonging to highlj^ 

 peculiar genera probably of very limited range, have been des- 

 cribed from the edge of the waterfalls at Khandalla. These are 

 Creninoconchus of the almost exclusively marine family lyittori- 

 nidae and Lithotis of the semi-terrestrial pulmonate family Suc- 

 cineidae. Our knowledge of both these interesting genera is due 

 primarily to the work of the late Dr W. T. Blanford.' In March 

 Lithotis was entirely absent from the cliffs from which it was 

 described. Its absence in the dry season is additional evidence for 

 the belief that, like other members of its family, it is an air- 

 breathing mollusc that can only exist in damp surroundings. In 

 dry weather it probably conceals itself and aestivates. Cremno- 

 conchus syhadreitsis, on the other hand, was found in great 

 abundance, but only at places where the cliff was shaded from 

 the midday sun and supported a growth of the peculiar dull green 

 filamentous alga on which it feeds. Some individuals were in 

 an active condition, crawling and feeding in the spray of the 

 falls; others, in drier places, were apparently quite torpid and had 

 their opercula tightly closed. A number of individuals in both states 

 were placed in jars of water. Some were prevented from reaching 

 the surface. These were drowned in 24 hours, dying partially ex- 

 panded. Others, placed in a jar with flat sides and only half full of 

 water, crawled out after a short time. Their movements could be 

 observed with great nicety through the glass. They moved upwards 

 slowly. When out of the water the shell was closely applied to the 

 glass except where the tentacles protruded in front, the ventral 

 surface of the body-whorl being in contact with it as well as the rim 

 of the aperture. The opening of the branchial cavity was patent, 

 but was relatively small and had a somewhat lunate form. It could 

 be easily seen that this cavity was full of water, and the animal 

 took with it a film of water that surrounded the shell on the glass. 

 After it had been moving about for some hours this film grew 

 smaller and finally disappeared. The orifice of the branchial 

 cavity was then shut, the foot retracted and the operculum closed. 

 The mollusc remained for days in this condition, absolutely im- 

 mobile, and probably would have so remained until it had been 

 soaked with water. Although the glass on which it crawled was 

 quite clean, it opened its mouth and thrust out its radula from 

 time to time, as though trying to scrape off its food, so long as it 

 remained active. Fig. 3, pi. IV, which shovvs the film of water, 

 the open branchial orifice, etc., was drawn from a specimen brought 

 alive but torpid to Calcutta and revivified by being placed in 

 water. 



Cremnoconchus seems, therefore, to be in a sense a water- 

 breather, incapable of obtaining its oxygen direct from the air, 

 but also incapable of obtaining it from water in the manner usual 



i Blanford, Ann. Mag. Nat. Hist., (3) XII, p. 184 (1863), and (4) III, p. 343 

 (1869). For Lithotis see al.so Gude, Faun. Brit. Ind. Moll., II, p. 457 (1914) ; 

 for Crem)ioconchiis, Stoliczka, Proc. As. Soc. Bengal, 1871, p. 108. 



