BY J. DOUGLAS OGILBY. 35 



proximal f of the pectoral spine. Gill-membranes meeting at a 

 very obtuse angle; width of isthmus about |- of the gill-slit; gill- 

 rakers 5 + 8, the longest rather more than ^ of the diameter of 

 the eye. Distance of dorsal fin from tip of snout 2| in the total 

 length ; dorsal spine granular in front, feebly serrated behind, 

 the sides coarsely striated, its length 4 of that of the head ; 

 adipose fin longer than high, as long as the dorsal, its distance 

 from which is 3^ in the total length : anal fin emarginate, higher 

 than long, its length | of the head : ventral rounded, | of the 

 head, and not quite reaching to the anal : pectoral with 10 soft 

 rays, the spine strong, similar to that of the dorsal, and f of the 

 head : upper caudal lobe much longer than the head, 3i in the 

 total length ; least depth of caudal peduncle 2i in its length 

 behind the adipose fin. Axillary pore minute. Vent midway 

 between the ventrals and anal. 



Silvery, the back strongly washed with blue. 



Etymology : — Named for Mr. George Masters, Curator of 

 the Macleay Museum, Sydney University, to whom I am indebted 

 for much valuable information on the fine collection under his 

 charge, and whose general knowledge of the Australian fauna is 

 possibly exceeded hj none. 



Type in the University Museum. 



Total length 2-55 millimeters. 



Distribution : — Northern Australia. 



From Arius fJialassinus, the only other oriental Tachisurid 

 which possesses three distinct groups of teeth on each side of the 

 roof of the mouth, A. mastersi differs in having a smaller eye, 

 larger mouth, wider patch of vomerine teeth, smaller, more widely 

 separated, oval patches of posterior palatines, longer maxillary 

 barbels, coarsely granular head-shields, shorter and broader nuchal 

 shield, larger saddle-shaped dorsal plate, granular humeral process, 

 coarsely striated dorsal spine, larger adipose fin, ifec. 



In outward appearance this species approaches more closely to 

 Sexanematiclithys sagor than to any other, but the presence of 

 distinct posterior palatine patches of teeth at once distinguishes 

 it therefrom, while — as compared with a Burmese example of 



