44 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



of the insufficiency of the description we are unable positively to assign 

 its place in the genus. It may possibly be identical with A. planiceps. 

 The type of the species cannot now be found in the Museum. 



10. Arius platypogon Giinther. 



Arius platypogon Giinther, Cat. Fishes Brit. Mus. v, 147, 1864 (San Jos6 de 

 Guatemala); Steindachuer, Ichthyol. Beitriige, iv, 17 (Magdalena Bay; 

 west coast Central America ; Callao). 



Habitat. — Pacific coast of tropical America, from Lower California 

 to Peru ; Magdalena Bay ; Mazatlan ; Libertad ; Punta Arenas ; San 

 Jose de Guatemala ; Panama; Callao. 



Head3| (4f); width of head 4f; depth 5| (Gf); length (28286) lo£ 

 inches. D. I, 7; A. 4, 14. 



Body rather elongate, the head not very broad nor much depressed, 

 a little broader than deep. Eye rather large, 5 to in head. Interor- 

 bital space slightly more than half head, a trifle less than width of 

 mouth ; length of snout 3i in head. 



Teeth all pointed; bands of vomerine teeth small, roundish, their 

 boundaries traceable by a slight depression in the young, in the adult 

 fully confluent with each other and with the palatine bands ; palatine 

 bands broad, ovate, several times as large as the patches on vomer, 

 continued backwards over the pterygoid region; premaxillary band 

 rather broad, 5 to C times as broad as long; maxillary barbel reaching 

 past base of pectoral in the young, not to gill-opening in the adult ; its 

 base a little broader and more compressed than usual in Arius; outer 

 mental barbels 2 in head ; inner 2£. 



Ante-dorsal shield very short, lunate, subtruncate in front, its breadth 

 more than three times its length on the median line. Occipital pro- 

 cess long, triangular, with straight margins, its length about If times 

 its width in front, its broad median line rather sharply heeled. In the 

 young it is proportionally shorter, little longer than broad. At the 

 beginning of this keel is the end of the long, narrow, groove-like fonta- 

 nelle, which extends forward to a point just behind the eye, where it 

 merges into the flattish and smooth anterior part of the head. Shields 

 of head all finely granular, the granules rarely forming distinct lines. 



Dorsal spine long, 1£ to Ih in head, the soft rays projecting beyond 

 the spine. Pectoral spine about as long as dorsal, sharply serrate be- 

 hind, the anterior seme not very sharp; axillary pore small or absent. 

 Ilumeral process nearly smooth, rather narrow and short, half length 

 of pectoral spine. Adipose fin short and rather high, its base barely 

 two-tifths length of base of anal. Caudal deeply forked, its upper lobe 

 longest, and slightly falcate, about as long as head. Ventrala reaching 

 anal in the females, shorter in the males. Vent nearer base of ventrals 

 than anal. 



Color in life very pale olive brown, with bronze and blue reflections; 



