236 A Review of American Species of Thread-fins. 



Habitat. South Atlantic and Gulf coast of North America. 

 Etymology, lini, eight, »3)ua, thread. 



Following the suggestion of Dr. Jordan, I have regarded Poly- 

 nemus octofilis Gill as the adult form of Polydactylus octonemus, 

 from which it differs only in having darker pectoral fins and shorter 

 pectoral filaments, differences which occur in other species of Poly- 

 dactijlus with age and no doubt in this one also. 



The specimens examined by me were taken by Dr. Gilbert at 

 Charleston, S. C, where it is vefy rare, entirely unknown to the 

 fishermen. 



5. Polydactylus opercularis. 



Trichidion opercularis Gill, Proc. Acad. Nat. Sci. Phila., 168, 1863 (Cape San 



Lucas). 

 Polynemus opercularis Giinther, Proc. Zool. Soc, 148, 1864 (copied) ; Giinther, 



Fish. Centr. Amer., 424, 1869 (copied) ; Steindachner, Ichthyologische 



Beitrage, IV, 9, 1875 (copied) ; Jordan & Gilbert, Bull. U. S. Fish. 



Com., 107, 111, 1882 (Mazatlan ; Panama); Jordan, Proc. U. S. Nat. 



Mus., 372, 1885 (Mazatlan ; Panama) ; Jordan, Cat. Fish. North 



America, 66, 1885. 

 Polynemus melanopoma Giinther, Fish. Centr. Amer., 421, 1869 (San Jose). 



Habitat. Pacific coast of Tropical America. 



Etymology. Latin, opercularis, from its dusky blotch on the operculum, found 

 also in most other species. 



This species is known to me from specimens dredged by the 

 "Albatross" in the ocean south of Panama. 



Recapitulation. 



The following is the list of the genera and species of the family 

 of Thread-fins {Polynemidae) recognized in this paper as occurring 

 in American waters : — 



1. Polynemus (Gronow) Linnaeus. 



1. Polynemus quinquarius Linnjeus. 



2. Polydactylus Lacepede. 



2. Polydactylus approximans (Lay & Bennett). 



3. Polydactylus virginicus (Linnaeus). 



4. Polydactylus octonemus (Girard). 



5. Polydactylus opercularis (Gill). 



