EIGENMANN: THE FRESHWATER FISHES OF BRITISH GUIANA 171 



Head 4-4.5; depth 5.25; dorsal 1,6; A. 10-13; adipose fin 3.5-4 in the length; 

 eye 3.33-4; interorbital 4.5; eye about in middle of the head. 



Occipital crest more than three times as long as wide, reaching the dorsal 

 plate; fontanels of about equal width, the posterior becoming narrower backward; 

 maxillary barbel reaching origin or end of base of anal; outer mental barbel to 

 near tip of pectoral or a little shorter. 



Dorsal low, rounded, the spine equal to the third or fourth ray, rough near 

 the tip in front and on the distal half of the posterior margin; space between the 

 dorsals much greater than the eye; caudal deeply forked, the lower lobe broader, 

 a little longer than the head, 3.5 in the length; ventrals not reaching anal ; pectorals 

 not to ventrals; pectoral spine equal to snout and eye in length or a little longer, 

 with minute teeth along its anterior margin to near the tip, with twelve long re- 

 curved spines along the middle of its posterior margin, the larger nearest the tip. 



An obscure lateral stripe; tip of caudal dusky. 



Pimelodus Lacepede. 

 Pimelodus Lacepede, Hist. Nat. Poiss., V, 1803, — (species of several genera). — ■ 



Cuvier, Regne Animal, II, 1817, 203 (species having a single band of teeth in the 



upper jaw). — Swainson, Class. Fishes, Amph., and Rept., II, 1839, 305 



(quadrimaculatus) . — Lutken, Dan. Vidensk.-Selsk., Skr., (5), XII, 1875, 163 



(macidatus = clarias). 

 Pseudariodes Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 99 (clarias). 

 Pseudorhamdia Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 101 (macidatus = 



clarias) . 

 Pseudorhamdia Lutken, Dan. Vidensk.-Selsk. Skr., (5), XII, 1875, 49, 169 (fur). 



Type, Pimelodus macidatus Lacepede. 



Eye with a free orbital margin; teeth on vomer none or minute; occipital 

 process reaching the dorsal plate; no parietal fontanel; head covered with thin skin, 

 granular; caudal forked; humeral process broad; barbels terete. 



Key to the Guiana Species of Pimelodus. 

 a. Adipose dorsal about 4 or more than 4 in the length. 



b. Occipital process broad at base, tapering to the dorsal plate. 



c. Pectoral spine smooth or nearly smooth in front. Dorsal without a conspicuous spot; sides 

 spotted, striped or plain; snout narrowed, its width less than half the length of the 

 head; posterior nares large; upper jaw but little projecting; dorsal spine reaching 



considerably beyond tip of last ray clarias. 



cc. Pectoral spine with antrorse teeth in front and retrorse teeth behind. Dorsal with a con- 

 spicuous black blotch near the middle of the front half of the fin; a light streak from 



