92 BULLETIN 189, UNITED STATES NATIONAL MUSEUM 



scarcely exceeding depth of caudal peduncle; caudal peduncle some- 

 what deeper than long, its depth 3.0 to 3.5 in head; head greatly com- 

 pressed, its dorsal outline slightly concave; snout scarcely as long as 

 eye, 4.2 to 4.6 in head; eye large, 3.4 to 4.1 ; interorbital narrow, 11.0 to 

 12.0; mouth oblique, superior, the mandible strongly projecting; 

 maxillary broad, about two-thirds width of eye, its lower margin con- 

 vex, rounded posteriorly, scarcely reaching middle of eye, 2.1 to 2.25 

 in head; mandible 1.95 to 2.0; teeth all minute, in a single series in 

 each jaw widely separated at midline, those on premaxillary widely 

 separated from the ones on maxillary, in broad bands on palatines, 

 pterygoids and tongue; giU rakers about two-thirds length of eye, well 

 separated, 11 or 12 on upper and 21 to 25 on lower limb of first arch; 

 scales thin, usually mostly lost in preserved specimens, with some- 

 what irregular margins; ventral scutes sharp, 23 or 24 in advance of 

 ventral fins, and 11 to 14 behind them; dorsal more or less over middle 

 of body, its origin about equidistant from tip of mandible and base of 

 caudal; caudal rather deeply forked, the lower lobe longer than the 

 upper; anal very long and low, its origin generally somewhat in ad- 

 vance of vertical from base of last ray of dorsal, its base 2.7 to 2.95 

 in length; ventral small about as long as eye, inserted about equi- 

 distant from base of pectoral and origin of anal; pectoral rather long, 

 reaching well beyond base of ventral, 1.35 to 1.5 in head, 5.0 to 5.3 

 in length. 



Color in alcohol bluish gray above; sides below level of upper 

 posterior angle of opercle silvery; upper surface of snout and tip of 

 mandible dusky; all fins, exclusive of the ventrals, with dusky points; 

 tips of dorsal and pectoral quite dark. 



This species is represented by a single specimen in the collection 

 furnished by the Mission, which was taken in the Gulf of Guayaquil 

 off Puerto Pizarro. This specimen ; one from the mouth of the Tumbes 

 River, Gulf of Guayaquil; three from the "West coast of South Amer- 

 ica," probably also from the Gulf of Guayaquil; and one from Guaya- 

 quil, Ecuador, form the basis for the foregoing description. These 

 range in length from 180 to 330 mm. (142 to 270 mm. to base of cnudal) . 

 They were compared with others from Panama Bay, the type locality, 

 with which they seem to agree in all respects. 



Range. — Panama Bay to the Gulf of Guayaquil in northern Peru. 



Genus OPISTHOPTERUS Gill, 1861 



Body elongate, very much compressed; chest and abdomen armed 

 with strong sharp bony scutes; mandible projecting; maxillary ending 

 somewhere under eye, not produced; teeth small, in a single series on 

 premaxillary, maxillary, and mandible, and in bands on palatines, 

 pterygoids, and tongue, none on vomer; dorsal fin small, placed behind 

 middle of body; anal very long, with about 50 to 60 rays; ventrals 



