CuAP. IV.] TEE TRITOXIA ARBOEESCEXS. 471 



might afford legitimate grounds for inferring the co-ex- 

 istence of the other in animals of the same class. 



Besides, it has been clearly established, that one at 

 least of tlie gasteropoda is furnished with the power of 

 producing sounds. Dr. Grant, in 1826, communicated 

 to the Edinburgh Philosopliical Society the fact, tliat 

 on placing some specimens of the Tritonia arborescens 

 in a glass vessel filled with sea water, liis attention was 

 attracted by a noise which he ascertained to proceed from 

 these mollusca. It resembled the " chnk " of a steel wire 

 on the side of the jar, one stroke only being given at a 

 time, and repeated at short intervals.^ 



The affinity of structure between the Tritonia and the 

 mollusca inhabiting the shells brought to me at Batti- 

 caloa, might justify the behef of tlie natives of Ceylon, 

 that tlie latter are the authors of the sounds I heard ; 

 and the description of those emitted by the former as 

 given by Dr. Grant, so nearly resemble them that I have 

 always regretted my inabihty, on the occasion of my visits 

 to Batticaloa, to investigate the subject more narrowly. At 

 subsequent periods I liave renewed my efforts, but with- 

 out success, to obtain specimens or observations of the 

 habits of the hving mollusca. 



The only species afterwards sent to me were Cerithia ; 

 but no vigilance sufficed to catch the desired sounds, and 

 I still hesitate to accept the dictum of the fishermen, as 

 the same mollusc abounds in all the other brackisli 

 estuaries on the coast ; and it would be singular, if 

 true, that the phenomenon of its uttering a musical 

 note should be confined to a single spot in the lagoon 

 of Batticaloa.''^ 



On lea\T.ng Batticaloa we liad to encounter still more 

 of the inconveniences to which travellers in Ceylon are 



^ Udmhurffh Philosophical Journ., 

 vol. xiv. p. l88. 



2 A letter whirli I received from 

 Dr. Grant on this subject, 1 have 

 placed in a note to the present chap- | full 



u II 4 



ter, in the hope that it may stinnilate 

 some other inquirer in Ceyhm to 

 prosecute the investigation which 

 I was imablo to carry out success' 



