eigenmann: the FRESHWATER PISHES OF BRITISH GUIANA 179 



Pirarara bicolor Spix, Gen. Spec. Pise. Bras., 1829, 23 (Amazon). 



No specimens of this species were preserved. Parts of a head were seen in 

 the Georgetown market. Schomburgk states that it reaches a length of four feet 

 and is "common to all rivers." The description is takan from Eigenmann and 

 Eigenmann. 



Head 3.33; depth 4.75; Br. 9; D. 1,7; A. 9; eye 9 in head, 3 in snout, 5 in inter- 

 orbital, 2 diameters behind the rictus. 



Body rapidly tapering towards caudal; head heavy, broad, flattened between 

 the eyes; greatest width of the head equals its length; width at the angle of the 

 mouth 2 in its length. 



Maxillary barbel on edge of lip, opposite anterior nostril, reaching beyond the 

 tips of the pectoral fin; mental barbels two-thirds to one-half as long as post- 

 mental barbels, which reach the pectoral. Lower jaw included; teeth all alike, 

 those on the intermaxillaries in a broad band of equal depth throughout; vomerine 

 teeth in a much broader patch; palatine teeth in narrower, wedge-shaped patches 

 contiguous to the vomerine patch. Gill-membranes separate to below anterior 

 margin of the eye. Gill-rakers short and fleshy, 4 + 15. Bones behind eye 

 variously grooved and granulated; the occipital process broadly rounded behind, 

 not meeting the reniform dorsal plate. 



Dorsal spine midway between snout and tip of adipose dorsal, and between 

 bases of pectoral and ventral fins; last dorsal ray over base of ventral, the length 

 of the spine 2.25 in head. 



Adipose dorsal short, high, its upper portion generally transformed into true 

 rays; its base longer than that of the anal. 



Caudal broad, slightly emarginate. The rays of the dorsal and caudal thick 

 and terete, once or twice branched. Ventrals extending for half their length 

 beyond the vent. 



Pectoral spine two or three times as thick as the dorsal spine, broad lamellae 

 in front and sharp recurved teeth behind; its length 2 in the head. 



Between pectorals and anal dark brown; lower part of head, a narrow band 

 above pectorals and along sides, spreading over the lower three-fourths of the tail, 

 white (yellow in life), region above this brownish; a round white spot on each side 

 of dorsal spine; orbit bordered with white above, head and ante-dorsal region with 

 darker spots or vermiculations; sometimes all of the lower parts are white. 



Brachyplatystoma Bleeker. 



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

 Brachyplatystoma Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 97 (vaManti). 



