1. POLYXEMUS. 323 



Description. — This is a third spoeius of Americim Poh/neiniihe, one 

 of which ouly was believed to occur in the troiiical parts of the 

 Atlantic. It is generically diii'erent from Pentanemus quinquarius, 

 and ma)- be readily distinguished from Polynemus plumieri by the 

 greater number of anal rays and by the narrow bands of the teeth on 

 the palate. 



The fish is moderately elongate ; its greatest height is between 

 the second dorsal and the anal, and one-foui'th of the total length ; 

 the tail is com])resscd and rather elevated, its height, above the end 

 of the anal, being 7| in the total length. The head is much longer 

 than high ; its length is 4| in the total ; its width between the eyes 

 is nearly one-fourth of its length. The snout is produced, obtusely 

 conical, and as long as the diameter of the eye. which is 4\ in the 

 length of the head. The cleft of the mouth is situated at the inferior 

 side of the head, as usual ; it is wide, the upper maxillary reaching 

 far behind the orbit, and its length being 2|- in that of the head. 

 The posterior margin of the praeoperculum is armed with a fine 

 serrature, and with a distinct spine above the angle, which forms a 

 produced, rounded, membranaceous lobe. The posterior extremity 

 of the opercular apparatus is membranaceous, rounded, and formed 

 by the operculum and siiboperculum. 



The origin of the fii\st(?o;'Sff? is in the vertical from the ninth scale 

 of the lateral line, or from the middle of the interspace between the 

 root of the pectoral and ventral fins. The fii'st spine is minute ; the 

 second is the strongest, all the others being flexible ; the third is the 

 longest, I3 in the length of the head ; the fourth is longer than the 

 second, and the following rapidly decrease in length. A series of 

 small scales ascends behind each spine nearly to the top. The di- 

 stance between the tAvo dorsals equals the length of the base of the 

 second, which is entirely covered with scales, and has the upper edge 

 emarginate ; the first and second rays are the longest, rather higher 

 than the spinous dorsal, and more than tliree times as long as the 

 posterior rays. The distance between this fin and the caudal is 5^ 

 in the total length. The caudal fin is entirely covered with scales, 

 deeply forked, \vith the lobes pointed, the upper of which is rather 

 lunger, and 3^ in the total length. The distance between the caudal 

 and anal fins is rather less than that between the caudal and dorsal, as 

 the extremity of the anal falls behind that of the dorsal, and in the 

 vertical from the 52nd scale of the lateral line. Its origin corre- 

 sponds to that of the dorsal ; it is entirely covered with scales, and 

 has the lower edge emarginate; the first two spines are very small ; the 

 third is nearly one-half the length of the first ray; the fij-st and second 

 I'ays are the longest, and three times as long as the fourteenth. The 

 length of the pectoral is one-sixth of the total ; its basal half is 

 covered with minute transparent scales. The free pectoral appendages 

 are rather feeble, and the uppermost is the longest, reaching nearly to 

 the tip of the pectoral. The root of the ventral falls behind the mid- 

 dle of the pectoral, in a vertical from tlie 12th scale of the lateral line ; 

 it Is short, one-eighth of the total lengtli, and reaches slightly beyond 

 the vent ; its spine is about one-half the length of the adjacent ray. 



