No. 5 (192 1 ) 



MADRAS AQUARIUM 



71 



" tail." The dirty khaki colour of Scyllanis appears to be of great 

 advantage in the struggle for existence, for they are very common 

 on the Madras coast where many are caught in those fishermen's 

 nets which sweep over the bottom. (See also page 93.) 



TANK No. 4. 



The File or Trigger fishes are represented here by several 

 species, a brown one called Balistcs iiiger (Tarn. Kuravaii), a deep 

 blue one, which appears however of rich plum colour by electric 

 light, B. crythrodon (Tam. Pcchchaikkiiravan), and a small orange- 

 banded species B. iiuditlatiis (Tam. Manjalvarikiiravau). Their 

 English names are due to the presence of a great rough file-like 

 spine in the first dorsal fin, that can be erected and locked in this 

 position. The flesh is poor and in ill-esteem. In many people it 

 produces poisonous effects, but the fishermen on this coast appear 

 to be immune and eat large numbers, at least of the sober-hued 

 species. It is possible that the more gaudy coloured species are the 

 poisonous forms, and if so, the colouration here is of a " warning " 

 nature. 



Fig. 7. — The Blue File-fish {Balislcs erythrodon). 



The Blue file-fish is exceedingly handsome, and has the 

 peculiarity of having red teeth ; the tail fin is strangely elongate 

 and crescentic in this species. When resting on the bottom it lies 

 over on one side. The smallest of these file-fishes, the striped 

 Balistes iiiidiilatiis, is extremely pugnacious towards its own kind; 

 if two are in the same tank — males probably — they often indulge 



