SOUTH AMERICAN NEMATOGNATHI. 429 



culatum and duodecimalis , and the name etentaculatum 

 should be retained. 



Depth a little less than the width. Head broad, high; 

 occipital roof-shaped, interorbital flattish. Snout in the 

 old rather pointed, its tip naked; interopercle erectile, 

 with a few shortish spines at its tip. 



Orbit 3-3|- in the snout, 6-6J in the head, 2i-2f in 

 the interorbital. Temporal keel distinct; posthumeral 

 keel strong; all the lateral scutes with a strong median 

 keel; ventral surface naked in the young, granular in 

 the adult. 



Base of the dorsal fin less than its distance from tip 

 of snout, its height 1J or more times in its base. 



Caudal obliquely emarginate, its outer rays thickened 

 and slightly prolonged. 



Pectoral reaching beyond base of ventrals; ventrals 

 little, if at all, beyond origin of anal fin. 



Light brown, spotted with darker, the belly spotted 

 with lighter; membrane of adipose fin black; outer cau- 

 dal rays barred, the remainder of the fin dusky; other 

 fins with very large dusky spots, the light background 

 forming reticulating lines. 



Head 2-J-2f; D. I, 11; A. 27-28. 



Four specimens .09-. 22 m. Rio San Francisco, below 

 the falls. 



400, Pterygoplichthys gibbiceps. 



Andstrus gibbiceps Kner, Hypos tomiden, 252, pi. 5, fig. 2, 1853 (Rio 



Negro). 

 Pterygoplichthys gibbiceps Giintlier, v, 252, 1864 (copied); Eigenm. 



& Eigenm. Proc. Cal. Acad. 2d Ser. ii, 44, 1889 (Coary; Teffe; 



Porto do Moz; Lago Alexo; Ctidajas; Lake Hyanuary; Santa- 



rem; Tabatinga; Lago do Maximo; Jutahy; Villa Bella; Silva; 



Obidos). 

 ChcKtostomus gibbiceps Steindachner, Flussfische Siidamerika's, ii, 



114, pi. iv, fig. 1, 1881'(Obidos; Villa Bella; Coary; Jatuarana; 



Gurupa; Tabatinga; Jutahy; Silva, Lake Saraca; Lake Hyanu- 



ary; Lago Alexo). 



