OCR Text |
Show 1003.] FISIIES OF THE GENUS TRIACANTIIUS. 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. T r ia c a n th u s Cuvier. Body compressed, covered with small rough scales; caudal peduncle more or less elongate, tapering; mouth small; teeth in 2 series in each jaw, 10 in each outer series, incisor-like; those of the inner series obtuse, rounded, 6 in the upper jaw, 2 in the lower. Branchiostegals 6 ; pseudobranchiae 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 represented by a strong spine, without soft rays; caudal widely forked. Vertebra* 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 base of anal half that of soft dorsal; D. V, 20-22 ; A. 15-16 ..................... I I . 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 4t-5 j times in total length; length of base of anal l f - l | times in that of soft dorsal; D. V, 2 2 -2 3 ; A. 1 6 -1 7 .......................................................... ........ b. Membrane between first two rays of spinous dorsal blackish; length of caudal peduncle 4 f -5 times in total length ; length of base of anal l f - l f times in that of soft dorsal; D. V, 23-24 ; A. 1 8 -1 9 ....................................... c. Membrane of spinous dorsal immaculate; length of caudal peduncle 6g-7 times in total length; length of base of anal 1| - 1 f times in that of soft dorsal; D. V r 2 1 -2 5 ; A. 1 7 -1 9 ........................................... ........ B, Snout straight; pelvis between ventral spines scarcely narrowed posteriorly; D. V, 24 -2 5 ; 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 ............ b. Membrane of spinous dorsal blackish; snout more than half as long as the head ; post-orbital part of head shorter than ej-e-diameter. c. Membrane between first two rays of spinous dorsal blackish ; snout less than half as long as the head.; postorbital part of head shorter than eye-diameter.................................................. 1. Tr. slrigilifer Cantor. 2. Tv. blochi Bleeker. 3. Tr. bicici'jleatus Bloch, 4. Tr. oxycephalus Bleeker. 5. Tr. brevirostris Schlegel. 6. Tr. indicus, n. sp. 7. Tr. nieuhofi Bleeker. |