1903.] FISHES OF THE GENUS TRIACANTHUS. 181 
postorbital part of the head from the vertical from the posterior 
margin of the eye to the gill-opening. Young specimens have a 
shorter snout, a deeper body, and longer dorsal and ventral spines 
than adults, and have been excluded from the diagnoses. In each 
case the total length of the largest example here described is given. 
TRIACANTHUS Cuvier. 
Body compressed, covered with small rough scales; caudal 
gees more or less elongate, t apering ; mouth small; teeth in 
2 series in each jaw, 10 in each outer series, incisor-like ; Enos of 
the inner series obtuse, rounded, 6 in the upper jaw, 2 in the 
lower. Branchiostegals 6; pseudobranchize present. Spinous 
dorsal with 5 rays, the first a long and strong spine; soft dorsal 
with 20-25 rays; anal with 15- 20 rays ; ventral fins each repre- 
sented by a strong spine, without soft rays; caudal widely forked. 
Vertebree 20. 
In all the species the colour is strikingly similar, being bluish 
grey above, silvery below. The only tangible differences in colour 
are that the membrane of the spinous dorsal fin is in some specimens 
immaculate, in others wholly or partly blackish. 
Key to the Species. 
I. Second ray of spinous dorsal more than half as 
long as the first, membrane of spinous dorsal 
immaculate ; length of yest of anal half that of 
soft dorsal ; D. V, 20-22; A. 16-16 ....... . 1. Dr. strigilifer Cantor. 
II. Second ray "of spinous dorsal less than half as 
long as the first. 
A. Snout concave; pelvis between ventral spines 
tapering to a distinct point posteriorly. 
a. Membrane of spinous dorsal immaculate; 
length of caudal peduncle 43-5}; times in 
total length ; length of base of anal 1{-14 
times in that of soft dorsal; D. V, 22-2 
A. 16-17 .. : 2. Ti. blochi Bleeker. 
6b. Membrane between first two rays ‘of spinous 
dorsal blackish; length of caudal peduncle 
4-5 times in total ‘Tength ; length of base 
of anal 12-18 times in that of soft dorsal; 
DV 23 —2ai ARGS O\ ee ed sas hdee adhe tsees 3. Tr. biaculeatus Bloch. 
c. Membrane of spinous dorsal immaculate ; 
length of caudal peduncle 63-7 times in 
total length; length of base of anal 13- 
1} times in that of soft dorsal; D. v, 
21 25; A. 17-19.. 4, Tr. oxycephalus Bleeker. 
B. Snout straight ; pelvis between ventral spines 
scarcely narrowed posteriorly ; D. V, 24-25; 
A. 18-20. 
a. Membrane of spinous dorsal blackish; snout 
half as long as the head; postorbital part of 
head not shorter than eye-diameter ......... 5. Fr. brevirostris Schlegel. 
6. Membrane of spinous dorsal blackish; snout 
more than half as long as the head; post- 
orbital part of head shorter than eye-diameter. 6. Tr. indicus, n. sp. 
c. Membrane between first two rays of spinous 
dorsal blackish ; snout Jess than half as long 
as the head ; postorbital part of head shorter 
than eye- -diameter De ee ee de ie mieunofu Bleeker. 
