Cuap. XI.] TRITONIA ARBORESCENS. 401 
pores, and other polypi, have yet to find a naturalist to 
undertake their investigation, but in all probability the 
new species are not very numerous. 
NOTE. 
TRITONIA ARBORESCENS. 
Tue following is the letter of Dr. Grant, referred to at page 
385 :-— 
Sir,—I have perused, with much interest, your remarkable 
communication received yesterday, respecting the musical 
sounds which you heard proceeding from under water, on the 
east coast of Ceylon. I cannot parallel the phenomenon you 
witnessed at Batticaloa, as produced by marine animals, with 
anything with which my past experience has made me ac- 
quainted in marine zoology. Excepting the faint clink of the 
Tritona arborescens, repeated only once every minute or two, 
and apparently produced by the mouth armed with two dense 
horny laminz, I am not aware of any sounds produced in the 
sea by branchiated invertebrata. It is to be regretted that in 
the memorandum you have not mentioned your observations 
on the living specimens brought you by the sailors as the 
animals which produced the sounds. Your authentication of 
the hitherto unknown fact, would probably lead to the disco- 
very of the same phenomenon in other common accessible 
paludine, and other allied branchiated animals, and to the 
solution of a problem, which is still to me a mystery, even 
regarding the tritonia. 
My two living tritonia, contained in a large clear colourless 
glass cylinder, filled with pure sea water, and placed on the 
central table of the Wernerian Natural History Society of 
Edinburgh, around which many members were sitting, con+ 
DD 
