EIGENMANN: THE FRESHWATER FISHES OF BRITISH GUIANA 181 



mouth, the post-mentals reaching beyond the ventrals. Dorsal and anal emar- 

 ginate, the first ray in each reaching beyond the tip of the last; dorsal and pectoral 

 spines slender, with recurved hooks on the posterior margin, most marked toward 

 the tip; pectoral and ventral falcate; caudal deeply forked, the outer rays normally 

 about 4 times as long as the middle ones, but prolonged in the young to equal the 

 length from snout to caudal. 

 Pale below, darker above. 



The young of this species can be readily distinguished by its long barbels 

 and prolonged caudal tips. 



Hemisorubim Bleeker. 

 Platystoma Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 27 (sp.), pre- 

 occupied in Diptera. 

 Hemisorubim Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 97 (platyrhynchos) . 

 Type, Platystoma platyrhynchos Cuvier and Valenciennes. 

 Upper jaw thin and truncate, shorter than the lower jaw; snout narrowed; the 

 width at the angle of the mouth 1.5 times in the greatest width of the head; mental 

 barbels approximate and near the edge of the lip; premaxillary band of teeth much 

 shallower at the middle than at the ends; the palatine patches large. Occipital 

 process shorter than the dorsal plate and meeting it; postorbital portion of the 

 head striate and granulate; skin on the sides of the head and snout reticulate. 



54. Hemisorubim platyrhynchos Cuvier and Valenciennes. 



Platystoma platyrhynchos Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 

 27 (no locality). — Muller and Troschel, in Schomburgk, Reisen, III, 1848, 

 628 (Rupununi). — Castelnau, Anim. Am. Sud, Poiss., 1865, 40 (Amazon). — 

 Kner, SB. Akad. Wiss. Wien, XXVI, 1857, 398 (Barra do Rio Negro). 



Hemisorubini platyrhynchos Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 97 (name 

 only). — Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), I, 1888, 138 

 (Manacapuru; Rio Negro; Montalegre; Rio Puty; Lago Alexo; Obidos; Coary; 

 Tabatinga; Hyavary; Tonantins; Sao Paolo) ; Occasional Papers Cal. Acad. 

 Sci., I, 1890, 206. — Eigenmann, Repts. Princeton Univ. Exp. Patagonia, III, 

 1910, 390. 



Hemisorubim platyrhynchus Gunther, Catalogue, V, 1864, 109 (copied). — Peters, 

 MB. Akad. Wiss. Berlin, 1877, 470 (Calabozo).— Cope, Proc. Am. Philos. Soc, 

 XVII, 1878, 674 (Peruvian Amazon).— Vaillant, Bull. Soc. Philom., (7), IV, 

 1880, 152 (Calderon). 

 No specimens of this species were obtained. 



