26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



greatest depth below a straight Hne extending through the lower mar- 

 gin of eye to middle of base of caudal ; caudal peduncle well com- 

 pressed, its depth 2.6 to 3.6 in head, 3.25 to 3.85 in greatest depth ; 

 head, length 3.0 to 3.5 in standard length, its depth 3.3 to 3.8; snout 

 3.9 to 4.4 in head ; eye 4.4 to 5.3 ; maxillary round posteriorly, reach- 

 ing about under posterior margin of pupil, 2.15 to 2.33 in head ; inter- 

 orbital (bone) 3.95 to 5.0 in head; upper section of opercle with feeble 

 radiating striae or none; mandible fully included in upper jaw, its 

 length 1.8 to 1.9 in head; gill rakers very long and slender, the long- 

 est ones in adults somewhat longer than snout, increasing in number 

 with age, about 137 in a specimen 160 mm. in total length, and about 

 225 in a specimen 285 mm. in total length; scales small, not closely 

 imbricated, exposed part of scale rather less than three times as deep 



Fig. 5. — Brcvoortia aurca, based on a specimen 280 mm. in total length, 225 mm. 

 in standard length (M.C.Z. No. 17831), from Rio Janeiro, Brazil. 



as long, the depth of the scale about 140 percent of its length, the 

 serrae not very long nor sharply pointed (see fig. 8, C; scale from a 

 fish about the same length as that in fig. 8, D), shorter and blunter in 

 smaller fish than in large ones, the scales much less reduced in size 

 on the back than in North American species, and scarcely reduced in 

 size at base of caudal, in fairly regular series; 7 longitudinal rows 

 of scales on side of caudal peduncle; the row of enlarged modified 

 scales on each side of median line on the back in front of dorsal fin 

 rather variable in number ; ventral scutes fairly strong, 1 7 to 20, usu- 

 ally 18, in front of ventral fins and 12 to 15 behind them; dorsal fin 

 moderately elevated anteriorly, the longest rays scarcely as long as 

 snout and eye, the last ray only a little longer than the immediately 

 preceding ones, the margin of the fin definitely concave, with a very 

 narrow sheath of scales at base, the origin of the fin generally about 

 equidistant from margin of snout and base of caudal ; caudal moder- 

 ately forked, rather short, the lower lobe a little longer than head. 



