igio.] N. ANNANDAI.E and J. T. JenkiNvS : Pledognathi and Pediculati. ii 



[h") Membrane of dorsal fin edged with black; first 

 dorsal spine not or barely longer than the head ; 

 snout slender, with the dorsal profile distinctly 

 concave and the ventral profile sinuous . . T. weheri. 



Tri acanthus strigilifer. Cantor. 

 Day, Faun. Brit. Ind., Fishes, vol, ii, p. 472. 



This species, which does not appear to be quite so common in the Bay of Bengal 

 as T. brevirostris , is easily distinguished by the length of the second dorsal spine. 

 Should this spine be broken, as is sometimes the case, the characteristic form of the 

 snout, midway between that of T. brevirostris and T. weberi, will serve as diagnostic. 



T. strigilifer has been taken on both sides of the Bay by the ' ' Golden Crown ' ' 

 and is represented in Day's collection. 



Triacanthus oxycephalus , Bleeker. 

 Bleeker, Atlas Ichthyologique, vol. v, p. go, pi. ccxx, fig. 3. 



This species is regarded by Günther as synonymous with T. biaculeatus, but is 

 apparently distinguished from the latter not only by the outline of its snout and the 

 great length of the anterior dorsal spine, but also by distinct differences in coloration 

 and in form of body. Prof. Max Weber has been kind enough to compare a specimen 

 withBleeker's original specimens. 



T. oxycephalus is not represented in Day's collection. It has been taken off the 

 coast of Orissa by the "Golden Crown " and also occurs off that of I^ower Burma as 

 well as in the Malay iVrchipelago. 



Triacanthus brevirostris, Temm. and Schleg. 



Day, Faun. Brit. Ind., Fishes, vol. ii, p. 471. 



T. brevirostris is perhaps the commonest species of the genus in the Bay of Bengal" 

 In Lake Chilka it occurs in brackish water. It is easily distinguished from other 

 species by its comparatively stout snout and by the almost complete blackness of the 

 membrane of the dorsal fin. 



Triacanthus weberi, Chaudhuri. 

 T weberi, Chaudhuri, Journ. Asiat. Soc. Bengal (N.S.), vol. vi, p. 497, pi. xxxii (1910). 



This species is not represented in Day's collection; indeed, all the specimens in 

 the collection of the Indian Museum were taken by the ' ' Golden Crown. ' ' Possibly it 

 inhabits rather deeper water than the other species. 



The peculiar form of the snout, which it is difficult to express accurately by 

 means of measurements, will at once distinguish the species. The dark pigment on 

 the snout, moreover, forms a narrower and better defined band on the sides than is 

 the case in T. strigilifer, T. brevirostris or T. oxycephalus. 



