EIGENMANN: the PYGIDIID^, a family of south AMERICAN CATFISHES. 325 



of opercle; snout about 2.5 in the head; nasal barbel reaching not quite to the tip of the maxil- 

 lary barbel; head nearly as wide as long; eye just in front of middle of the head. 

 6. Head 6 in the length; the first pectoral ray with its filament equals the length of the head; sides 

 and back with numerous spots, each larger than the eye, in about five series between the dorsal 



and anal; origin of dorsal equidistant from tip of caudal and eye 44. guianense Eigenmann. 



66. Head 5 in the length; first pectoral ray with its filament equals the length of the head without the 

 opercle; uniform yellowish-brown above, lighter below, top of head marbted; origin of dorsal 



nearer tip of caudal than eye 45. conradi Eigenmann. 



aa. Origin of anal under origin of dorsal. 



c. Head 6 in the length; maxillary barbel reaching tip of pectoral; upper parts obscurely spotted; 

 origin of dorsal equidistant from tip of caudal and middle of pectoral; eye in anterior half of 



Ijg^jj 46. gracilior Eigenmann. 



cc. Head 7 in the length; maxillary barbel reaching middle of pectoral; eye entirely in anterior half 



of the head, nearly equal to the interocular and to the snout. . .47 amazonicum (Steindachner). 



ccc. Head 5.5 in the length; maxillary barbel reaching tip of last interopercular spine; eye entirely in 



anterior half of the head, considerably less than the interorbital or the snout; opercular and 



interopercular bunch of spines alike 48. hasemani Eigenmann. 



44. Pygidium guianense Eigenmann. (Plate L, fig. 1.) 

 Pygidium guianense Eigenmann, Ann. Carnegie Mus., VI, 1909, p. 11; Eigenmann, 



Reports Princeton Univ. Exped. Patagonia, III, 1910, p. 400; Mem. Carnegie 



Mus., V, 1912, p. 212 (Aruataima Cataract above Holmia.) 



Habitat. — Upper Potaro River, British Guiana. 

 1003, C. M., type, 77 mm. Aruataima Cataract. Eigenmann. 



Head 6; depth equals head in length; D. 9; A. 7; eye 4 in snout, 9.5 in head; 

 head nearly as broad as long; maxillary barbel reaching to tip of opercle; teeth in 

 bands of about four irregular series; origin of anal under middle of dorsal; dorsal 

 fulcra extending forward to near the dorsal; caudal rounded; first pectoral ray pro- 

 longed in a filament nearly as long as the rest of the ray; round dark spots every- 

 where, except on belly and lower surface of head; caudal dusky, the margin light. 



45. Pygidium conradi Eigenmann. (Plate L, fig. 2.) 

 Pygidium conradi Eigenmann, Mem. Carnegie Mus., V, 1912, p. 212 (Amatuk and 



Waratuk Cataracts). 



Habitat. — Lower Potaro River, British Guiana. 

 2212, C. M., 41 mm., type. Amatuk Cataract. Eigenmann. 

 11710, I. U. M., 34 mm., paratype. Waratuk Cataract. Eigenmann. 



With the characters given in the key. 



The teeth conic. 



