BULLETIN OF THE UNITED STATES FISH COMMISSION. 321 



B(xly moderately elongate, compressed, the back not elevated ; head 

 compressed ; snout rather short, not prominent ; anterior profile slowly 

 rising- from snout to front of dorsal. Premaxillaries extending beyond 

 front of snout, anteriorly on the level of the upper part of the pupil. 

 Mouth large, very oblique, the maxillary extending to below the middle 

 of the eye, its length 2^ in head. Lower jaw strongly projecting at tip. 

 Chin without pores. 



Front of premaxillaries with a long, sharp, curved canine on each side 

 (one of these often smaller or absent) ; sides of upper jaw with smaller 

 teeth, wide-set, mostly in one row. Lower jaw with about two series 

 of small, slender teeth in front ; laterally with a single series of small 

 teeth, besides three to six large canines, much smaller than the canines 

 of the upper jaw. 



Preorbital narrow, not wider than the pupil. Eye large, 4.J in head, 

 slightly shorter than snout, which is about equal to interorbital width. 

 Preopercle with a membranaceous flap at its angle, which is striate and 

 slightly fringed at its edge. Gill-rakers rather long and slender, few 

 in number. Pseudobrauchise well developed. Xostrils small, the pos- 

 terior vertically oblong. 



Scales small, nearly smooth, deciduous. Dorsal and anal fins closely 

 covered with small scales. Lateral line little arched, becoming straight 

 behind vent. First dorsal small, its spines slender, the highest 2J in 

 length of head. First spine minute or obsolete, the second not much 

 shorter than third. Space between dorsal fins about equal to diameter 

 of eye, 3i in head. Soft dorsal moderate, its longest ray a little less 

 than one-third length of head. Caudal shortish, slightly double-concave, 

 its middle rays about half length of head. Base of anal two-thirds 

 length of head, its spines rudimentary. Yentrals half length of head, 

 reaching half way to vent, -which is close in front of anal. Pectorals 

 reaching considerably beyond tips of A'entrals, their length l^ to 1^ in 

 head, 4^ to 4^ in body. Flesh comparatively soft. 



Color in life : Bluish gray above ; grayish silvery below ; top of snout 

 and tip of lower jaw blackish ; inside of mouth yellow, with black on 

 lower lip within ; lining of opercles black, bordered with pale orange. 

 Dorsals, caudal, and pectorals with fine black punctulations; the ground 

 color in all except the spinous dorsal faintly yellowish. Anal white, 

 the anterior part and the tips of most of the rays yellowish, punctate 

 Avith black. Ventrals white, immaculate. A dark blotch behind orbit 

 and another on upper part of opercle. Axil brown above, the color ex- 

 tending on the upper rays of the pectoral Avithin. 



This species seems to be rather common at Panama, where numerous 

 specimens were obtained. It is extremely close to 1. affinis Steind. from 

 Porto Alegre, Brazil, and -were it not for the considerably longer i)ec- 

 toral, we should consider- it identical with the latter species. IsojJisthus 

 parvipirMis (C. & V.) Gill, from Surinam, is insuificiently described, but 

 seems to be nearer I. affinis, if not identical with it. 



Bull. U. S. F. c", 81 21 Jfiiaie 9,18 82, 



