396 MEMOIRS OF THE CARNEGIE MUSEUM 



the caudal; skull very short above, the profile depressed over the eyes; mouth very 

 oblique; maxillary slipping under the suborbital; maxillary-premaxillary border 

 three-fourths of the length of the head; gill-rakcrs short, tubercular, about eighteen 

 on the lower arch. 



Scales cycloid, very small along the back, becoming larger downward; basal 

 half of anal scaled; caudal naked; lateral line straight. 



Pectorals very large, wing-like; ventrals about one-fourth as long as the pec- 

 torals; anal very long, its margin straight, its origin equidistant from the angle of 

 the mouth and the end of the anal; dorsal small, over the anterior part of the anal; 

 caudal lunate, its middle rays prolonged. Iridescent silvery; a large black humeral 



spot. 



Hydrolycus Mtiller and Troschel. 



Hydrolycus MtJLLER and Troschel, Horae Ichth., I, 1845, 18. 



Type, Hydrocyon scomberoides Cuvier. 



Distinguished by its rounded caudal and short anal. Dorsal in advance of 

 anal; anal and caudal scaled; scales with serrate margins. 



Of the three species of this genus one is said to occur in all the rivers of Guiana. 

 We did not secure specimens. 



252. Hydrolycus scomberoides (Cuvier). 



Hydrocyon scomberoides Cuvier, Mem. Mus. d'Hist. Nat., V, 1819, 357, pi. 27, 



% 2. 

 Hydrocynus scomberoides Cuvier, Regne Animal, II, 1817, 168. 

 Hydrolycus scomberoides Mijller and Troschel, Horse Ichth., I, 1848, 19, pi. 5, 



fig. 2; in Schomburgk, Reisen, III, 1848, 636 (all streams). — Eigenmann and 



EiGENMANN, Proc. U. 8. Nat. Mus., XIV, 1891, 59.— Fowler, Proc. Acad. 



Nat. Sci. Phila., 1906, 466. — Eigenmann, Repts. Princeton Univ. Exp. 



Patagonia, III, 1910, 444. 

 Cynodon scomberoides Cuvier and Valenciennes, Hist. Nat. Poiss., XXII, 1848, 



324 (Essequibo). — Kner, " Familie der Characinen," ii, 1848, 45 (Bananeira). 



— Castelnau, Anim. Am. Sud, Poiss., 1855, 75, pi. 39, fig. 2 (Araguay; Lac 



de Jules). — GtJNTHER, Catalogue, V, 1864, 358 (River Capin, British Guiana). 



— Peters, MB. Akad. Wiss. Berhn, 1877, 472 (Calabozo). — Steindachner, 



"Flussfische Siidamerika's," iv, 1882, 15 (Iquitos, Amazonas). 

 ? Hydroscion ? armahis Schomburgk, Fishes Brit. Guiana, I, 1841, 247, pi. 25bis.^^ 



'= There are two plate.s marked 2.5. Only the second belongs to this .s]5ocics. The dcscrijition evidently 

 refers to tliis species. 



