238 MEMOIRS OF THE CARNEGIE MUSEUM 



The pectoral thorns are 17, 18, 22, and 23 in different specimens, the largest 

 number being found in 7542 M. C. Z. from Manacapuru. It is quite possible 

 that most of the specimens from north of the Paraguay basin heretofore referred 

 to P. gracilis really belong to this species. The specimens at present in the Museum 

 of Comparative Zoology are : 



7566a-b. 95-126 mm. to base of caudal, Maues, Rio Madeira. Thayer Expedi- 

 tion. 

 7487a.i- 190 mm.. Para. Thayer Expedition. 

 7472a. 172 mm., Cudajas. Thayer Expedition. 

 75G7rt. 137 mm., Santarem. Thayer Expedition. 

 7588a. 154 mm., Rio Puty. Thayer Expedition. 

 7542a. 212 mm., Manacapuru. Thayer Expedition. 



4. Pimelodella gracilis (Cuvier & Valenciennes). 



Pimelodus gracilis Cuvier & Valenciennes, His. Nat. Poiss., XV, 1840, p. 181 



(Buenos Ayres; Parana at Corrientes); Valenciennes, Voy. d'Orbigny, Vol. 



V, 1847, Poissons, p. 6, plate II, fig. 5; Kner, Sb. Ak. Wiss. Wien, XXVI, 



1857, p. 418 (Caigara, Mattogrosso; Rio Guapore; Cujaba); Gunthbr, Cat. 



Fishes Brit. Mus., V, 1864. p. 121; Boulenger, Trans. Zool. Soc, 1896, p. 27 



(Descalvados) . 

 Pimelodus {Pseudorhamdia) gracilis? Steindachner, Flussfische Siidam., I, 1879, 



p. 9 (Orinoco near Ciudad Bolivar). 

 Pimelodella gracilis Eigenmann & Eigenmann, Proc. Cal. Acad. Sci., (2), I, 



1888, p. 132 (Goyaz); ? Occasional Papers Cal. Acad. Sci., I, 1890, p. 153; 



Proc. U. S. Nat. Mus., XIV, 1890, p. 29; Ann. Carnegie Mus., IV, 1907, 



p. 114, pi. XXXII, fig. 2 (Corumba; Laguna Ypagarai); Eigenmann, Reports 



Princeton Univ. Exped. Patagonia, III, 1910, p. 389. 

 Rhamdia gracilis Ribeiro, Fauna Bras., Peixes, IV, 1912, p. 269. 

 Pimelodus lateristriga Boulenger (non Miiller & Troschel), Trans. Zool. Soc. Lond., 



1896, p. 27 (Descalvados). 

 Pimelodus {Pimelodella) tmniophorus Regan, Ann. and Mag. Nat. Hist. (7), XII, 



1903, p. 625 (Descalvados). 



Habitat.^La. Plata Basin; Uruguay Basin; ? Amazon; ? Orinoco. More 

 abundant in the La Plata Basin than elsewhere. 



In 6947 the maxillary barbel in specimens between 78 and 112 mm. long extends 

 beyond the base of the caudal; in the specimens 97 mm. long to the end of the 



" In this specimen the dorsal spine is very high, equal to the length of the head. Pectoral thorns 22. 



