178 MEMOIRS OF THE CARNEGIE MUSEUM 



Eye 4.5-5.5, 1.3-1.5 in interorbital, somewhat behind the middle of the head; 

 premaxillary teeth in a narrow band of the same width throughout. Maxillary 

 barbel extending to the middle of the caudal or farther, post-mental not quite to 

 tip of pectoral. 



Dorsal spine with retrorse notches in front, roughened behind, about equal 

 to snout and eye in length; pectoral spine strong, striate above and below, with 

 antrorse teeth in front and retrorse teeth behind; adipose fin nearly or quite half 

 as long as the body without the head; caudal peduncle half as high as long. 

 Caudal slightly notched, the upper lobe shorter than the lower, projecting for 

 about one-fourth of its length beyond the fork. 



A dark saddle downward and forward from front of dorsal, covering nearly 

 the entire opercle; an irregular mottled dark band along the lateral line and just 

 below it; base of caudal dark, the fins irregularly mottled. Lower surface white. 



Phractocephalus Agassiz. 



Phractocephalus Agassiz, Selecta Gen. et Spec. Pise. Bras., 1829, 22 (bicolor = 



hemilopterus) . 



Large. Vomer with a large pentagonal patch of teeth in contact with the 

 palatine patches. Occipital process large, semicircular, not meeting the reniform 

 dorsal plate. Upper half of adipose usually rayed. Barbels subterete. Caudal 

 forked; head as broad as long. 



Type, Silurus hemiliopterus Bloch and Schneider. 



52. Phractocephalus hemiliopterus (Bloch and Schneider). 



Silurus hemiliopterus Bloch and Schneider, Syst. Ichth., 1801, 385. 



Phractocephalus hemiliopterus Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 

 1840, 3, pi. 421. — Schomburgk, Fishes Brit. Guiana, I, 1841, 169 (Guiana, 

 everywhere). — Muller and Troschel, in Schomburgk, Reisen, III, 1849, 643 

 (all rivers of Guiana). — Castelnau, Anim. Am. Sud, Poiss., 1855, 47, pi. 15, 

 fig. 4 (Rio Crixas; Araguay; Amazon). — Gunther, Catalogue, V, 1864, 110 

 (River Cupai) .— Vaillant, Bull. Soc. Philom., (7), IV, 1880, 152 (Calderon).- 

 Cope, Proc. Am. Philos. Soc, XVII, 1878, 674 (Peruvian Amazons). — Eigen- 

 mann and Eigenmann, Proc. Cal. Acad. Sci., (2), I, 1888, 135 (Xingu; Coary; 

 Teffe; Manacapuru; Obidos ; Lake Hyanuary) ; Occasional Papers Cal. Acad. 

 Sci., I, 1890, 188. — Eigenmann, Repts. Princeton Univ. Exp. Patagonia, III, 

 1910, 390. 



Phractocephalus bicolor Agassiz, Selecta Gen. et Spec. Pise. Bras., 1829, 23 (Amazon). 



