SOUTH AMERICAN NEMATOGNATHI. 321 



Cetopsis ccecutiens Agassiz, Gen. et. Spec. Pise. 12, 1829; Cuv. & Val. 

 xiv, 384, 1839 (copied); Kner, SB. Ak. Wieii, xxvi, 409, 1858. 

 Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. i, 157, 1888 

 (Gurnpa). 



Cetopsia cacutkna QilntheT, Cat. v, 199, 1864 (Kiver Cupai, tribu- 

 tary to the Amazon, 800 miles from the sea). 



Habitat: Lower Amazon; Gurupa to Eio Cupai. 



Body heavy, little compressed, tapering rapidly to the 

 caudal peduncle. Head bluntly conical, the bones 

 everywhere covered with a thick layer of muscle. Pro- 

 file arched, depth of the head considerably greater than 

 its width. Anterior nares situated near the lip, four 

 times as wide apart as the posterior nares which are 

 large, oval, above the anterior margin of the eye. 



Eye small, rudimentary, covered with skin, not larger 

 than the posterior nares. 



Maxillary barbels almost entirely concealed in a slit- 

 like groove, 3?> in the length of the head. Mental and 

 postmental barbels of about the same length disposed as 

 two pairs behind the angle of the mouth, receivable in 

 shallow grooves. 



Mouth inferior, its width at the rictus 2J in the head; 

 a narrow band of fine villiform teeth on the intermax- 

 illaries; mandible and vomer each with a single series 

 of firmly set, thick compressed teeth. 



Opercle with a broad membranaceous border. Gill- 

 opening extending farther below than above the upper 

 pectoral ray. 



Pectoral pore an elongate slit; lateral line straight, 

 simple. 



Distance of dorsal spine from the snout 2| in the 

 length, first dorsal ray somewhat elongate, the rays 

 rapidly decreasing in height backward, the last not a 

 third as high as the second. 



Caudal deeply emarginate, 4| in the length. 



Anal rays decreasing in height backward. 

 21 " 



