234 A Review of American Species of Thread-fins. 



aa. Pectoral Jilaments 7 : 



Body deep, compressed, anterior profile nearly straight ; maxillary 2^ in 

 head ; length of snout 5 in head ; eye large, equal to interorhital space, 

 5 in head. Scales moderate. Longest dorsal spine equal to longest ray 

 of soft dorsal and 1^ in head ; caudal lobes about as long as head ; pecto- 

 ral fin 1^ in head ; pectoral filaments somewhat longer than head, reach- 

 ing to front of anal fin, in adult. Color yellowish-white, darker above ; 

 scales on back with dark punctulations on their margins ; the young 

 silvery-white. Head 3^ in length ; depth 3^; D. VIII— I, 9 to 12; A. Ill, 

 13 or 14; Scales 7 — 71 — 10 virginicus, 3. 



aaa. Pectoral Jilaments 8 or 9. 



h. Maxillary less than ^ length of head ; pectoral filaments 8 ; body somewhat 

 compressed, elongated, anterior profile nearly straight, little declined. 

 Head much compressed, gape oblique ; snout 5 in head ; eye less than 

 iuterorbital space, 4^ in head. Scales rather small. Longest dorsal 

 spine 1^ in head; longest ray of soft dorsal 1-| in head; caudal lobe 

 slightly longer than head, 3^ in body ; pectoral fins 1^ in head ; pectoral 

 filaments reaching to vent in^dult (octojilis), longer in young (octonemus). 

 Color light olivaceous, tinged with dark punctulations ; belly whitish ; 

 pectoral black in adult, pale in young. Head 3^ in length ; depth 3y ; 

 D. VIII— I, 12 or 13 ; A. Ill, 13 to 15 ; Scales 6—70—10. 



octonemus, 4. 



lb. Maxillary more than i length of head ; pectoral filaments usually 9 ; body 

 elongate, compressed, outline from spinous dorsal to snout slightly con- 

 vex, and little declined. Head much longer than high ; snout conical, 

 7 in head ; eye rather large, about 5 in head. Scales of small size. 

 Longest dorsal spine 1§ in head ; longest ray of soft dorsal 1| in head ; 

 caudal lobes slightly longer than head ; pectoral fin as long as head 

 behind pupil ; pectoral filaments reaching near front of anal fin in adult. 

 Color greenish-brown above and yellowish-green below. Head 3^ in 

 length ; depth 3| ; D. VIII— I, 12 ; A, III, 13 ; Scales 8—69 or 75—13. 



opercularis, 5. 



2. Polydactyliis approxinians. 



Pohjnemus approximans Lay & Bennett, Beechey's Voyage, Zool. Fish., 57, 1849 

 (Mazatlan) ; Giinther, Fish. Centr. Anier., 423, 18G9 (Chiapam ; 

 Panama) ; Jordan & Gilbert, Proc. U. S. Nat. Mus,, 365, 376, 1882 

 (Panama); Jordan k Gilbert, Bull. U. S. Fish. Com., 107, 111, 112, 

 1882 (Mazatlan; Panama; Puntas Arenas); Steindachner, Ichthyo- 

 logische Beitriige, IV, 8, 1875 (copied) ; Jordan, Proc. U. S. Nat. Mus., 

 372, 1885 (Mazatlan ; Panama) ; Jordan, Cat. Fish. N. Amer., 66, 

 1885 ; Jenkins & Evermann, Proc. U. S. Nat. Mus., 1888 (Guaymas). 



Trichidion approximans Gill, Proc. Acad. Nat. Sci. Phila., 258, 1862 (Cape San 

 Lucas) ; 169, 1863 (Panama). 



