232 A Review of American Species of Thread-fins. 



and anterior portion of several filiform articulated appendages, free 

 from each other, said to be organs of touch. In the young, the 

 dorsal, caudal, and pectoral fins are dusky, the anal and ventral fins 

 white ; all the fins grow darker with age, the pectorals usually be- 

 coming black, the operculum blackish. Bones of the skull with a 

 well-developed muciferous system as in Scisenidse. " Basis cranii 

 double, with tube ; post-temporal bifurcate ; scapula with median 

 foramen ; superior pharyngeal bones 4. Brachial ossicles divided ; 

 two normal, supporting the dorsal fin, one longitudinal without 

 rays, and one a plate on the coracoid, supporting the pectoral fila- 

 ments." {Cope.) Stomach coecal, with a few pyloric appendages. 

 Air-bladder various, sometimes wanting. Yertebrte 24. Genera 4, 

 Galeoides, Folistonemus, Polynemus, and Polydactijlus, the last two 

 only are found in America ; species about 25, of which 5 are found 

 in America. Inhabit tropical seas, and entering rivers. Most of 

 them are valued as food fishes. 



This peculiar family constitutes the group or suborder Rhcrj- 

 nopteri, characterized chiefly by the peculiarities of structure and 

 attachment of the pectoral fin. Its relations appear to be with the 

 Scisenidse on the one hand and with the Mugilidse on the other, but 

 these resemblances may be superficial. 



Analysis of American Genera of PoLYNEMiDiE. 



a. Anal fin much longer than soft dorsal, of about 30 rays; vomer without 

 teeth ; preoperculum entire ; free filaments of pectorals longer than body. 



Polyneiuiis, 1. 



aa. Anal fin not mu(!h longer than soft dorsal, of about 13 or 14 rays ; vomer 

 with teeth ; preoperculum serrate ; free filaments of pectorals mostly 

 shorter than body Polydactyllis, '2. 



Genus I. POLYNEMUS. 



Polynemm Gronow, Mus. Ichthyol. 31, 1754 ((jniiif/itnrius). 



Pentaneinus Artedi, Sebje Thesaurus, III, 74, 1758 (rpiiiK/iiarins). 



PohjnemuK Linnffius, Syst. Nat., Ed. X, 317, 1758 (in part ; quinr/uarius ; virgini- 



cus; paradiscnus). 

 Pentanemux G until er (^fniinquaruis) . 

 Polynemus Gill, Proc. Acad. Nat. Sci. Phila., 272, 18C1 ((/uinijuarius). 



Type. Polynemus quinquarius Linnseus. 



Etymology. 7ro^uf, many ; v^jua, thread. 



