168 MEMOIRS OF THE CARNEGIE MUSEUM 



Type, Pimelodus cristatus Muller and Troschel. 



Similar to Pimelodus, but with a parietal fontanel persistent throughout life; 

 the occipital process not tapering, but of nearly uniform width, in contact with 

 the dorsal plate behind; no vomerine teeth. 



Species usually slender and of small size. 



Key to the Guiana Species of Pimelodella. 

 a. Adipose fin 2.33-2.5 in the length. A narrow lateral band, conspicuous in young, becoming obscure 



with age. Maxillary barbels to below middle of adipose or beyond tip of caudal cristata. 



aa. Adipose fin 3 or more in the length. 



b. Eye 2.5 in the head, longer than snout; interorbital 2 in the eye; maxillary barbel reaching end of 

 adipose or caudal; caudal lobes long, slender, the lower 3 in the length; pectoral spine little 



shorter than head megalops. 



66. Eye 3.5 in head, shorter than snout; tip of dorsal dusky; maxillary barbel reaching middle of 

 adipose; pectoral spine about equal to snout and eye macturki. 



44. Pimelodella cristata (Muller and Troschel). 



? Pimelodus insignis Schomburgk, Fishes Brit. Guiana, I, 1841, 180 (not plate). — 

 Muller and Troschel, in Schomburgk, Reisen, III, 1848, 643 (Takutu and 

 Rio Branco). 



Pimelodus cristatus MtJLLER and Troschel, in Schomburgk, Reisen, III, 1848, 628 

 (Takutu and Mahu Rivers) ; Horse Ichth., Ill, 1849, 4 (Guiana, in Esse- 

 quibo). — GtJNTHER, Catalogue, V, 1864, 117 (Guiana; Essequibo; River Capin, 

 Para).— Vaillant, Bull. Soc. Philom., (7), IV, 1880, 152 (Calderon) .— Stein- 

 DACHNER, " Flussfische Siidamerika's," iv, 1882, 4 (Rio Huallaga). — ? Perugia, 

 Ann. Mus. Genova, (2), X, 1891, 631 (Tucuman). 



Pimelodella cristata Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), 1, 1888, 

 132 (San Gonyallo; Avary; Villa Bella; Jutahy; Tapajos; Rio Mucuri; 

 Tabatinga; Hyavary ; Coary) ; Occasional Papers Cal. Acad. Sci., I, 1890, 150. — 

 Eigenmann and Bean, Proc. U. S. Nat. Mus., XXXI, 1907, 660 (Amazon).— 

 Eigenmann, Repts. Princeton Univ. Exp. Patagonia, III, 1910, 388. 



Pimelodus agassizii Steindachner, '' Icthj^ologische Beitrage," v, 1876, 99 

 (Peruvian Amazon; Hyavary). 



Pimelodus (Pseudorhamdia) wesselii Steindachner, " Siisswasserfische Siidostlichen 

 Brasilien," iii, 1876, 56, footnote (Essequibo). 



? Pimelodella wesselii Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), I, 

 1888, 132 (Cudajas; Para; Marajo; Rio Madeira; Rio Puty; Santarem); 

 Occasional Papers Cal. Acad. Sci., I, 1890, 152. 



Pimelodus ophthalmicus Cope, Proc. Am. Philos. Soc, XVII, 1878, 675 (Upper Ama- 

 zon). 



