4 1 8 Memoir Sears Foundation for Marine Research 



- Body quite slender, rather strongly compressed, its greatest thickness about 2.5 

 times in its depth, its greatest depth 3.3—4.65 in SL; the dorsal outline gently convex, 

 the ventral outline much more strongly convex. Caudal peduncle rather strong, its 

 depth 2.7—2.8 in head. 



Scales adherent; those on middle of side below anterior rays of dorsal definitely 

 deeper than long, without vertical grooves, closely imbricated-, the exposed part rather 

 more than two times deeper than long: the membranous margin only slightly irregular. 

 Ventral scutes moderately developed, 22 or 23 in advance of pelvic fins and 10 or 

 1 1 behind them. 



Figure 104. Ilisha altamaxonica, 360 mm TL, 275 mm SL, Amazon River somewhere between Para and 

 Mangos, Brazil, USNM 52548. Drawn by Ann S. Green. 



Head 3.7—3.9 in SL, its depth at vertical from slight crossgroove at occiput 4.25— 

 4.65. Snout only a little shorter than eye, with a prominent median notch, 2.0-2.05 

 in head. Eye with much adipose tissue, 3.9-4.3. Interorbital 2.0-2.15 ^^ head. 

 Cheek deeper than long. Maxillary rather narrowly rounded posteriorly, reaching 

 below middle of eye, 2.0—2.05 '" head; a narrow bone with teeth between premaxillary 

 and maxillary. Mandible projecting strongly, its tip scarcely below dorsal outline of 

 head, its margin within mouth rising gently, 1.8— 1.85 in head. Gill rakers at angle 

 of first arch about 75 "/o of length of eye, only 12 or 13 on lower limb. Teeth small, 

 in a single row, on anterior part of mandible and on premaxillaries ; minute teeth on 

 margin of maxillary, and still smaller teeth on the bone between premaxillary and 

 maxillary; bands of minute granular teeth on palatines, pterygoids, and tongue. 



Dorsal fin rather high anteriorly, its longest rays reaching far beyond the tip of 

 last ray if deflexed, its origin equidistant between margin of snout and base of caudal, 

 or a little nearer to snout, its distance from margin of snout 1.9—2.0 in SL; a sheath 

 composed of a single row of scales at its base. Caudal fin well forked, the lower lobe 

 much the longer; small scales extending onto the fin, covering most of it. Anal fin long, 

 with a definite lobe anteriorly, its origin immediately behind a vertical from last dorsal 

 ray, only a little nearer to margin of opercle than to base of caudal, its base 3.2—3.4 



