172 CALIFORNIA ACADEMY OF SCIENCES. 



plate i, figs. 1-3, 1847 (La Plata to Mexico, Lake Maracaibo); 

 Cuv. & Val. Hist. Nat. Poiss. xv, 192, 1840 (Cayenne; Mara- 

 caibo); Schomburgk, Fishes of Guiana, part i, 175, 1841 (Kivers 

 of Guiana generally; Rio Negro; Amazon); Steindachner, SB. 

 Ak. Wien, Ivi, 1867, Ichthyol. Notiz. vi, 32 (La Plata); Stein- 

 dachner, SB. Ak. Wien, Ix, 1869, Ichthyol. Notiz. ix, 6 (Monte- 

 video); Hensel, Wiegm. Arch. 1870, i, 69 (Jacuhy); Liitken, 

 Dan. Selsk. Skr. 163, fig. 1875 (Rio das Velhas); Steindachner, 

 SB. Ak. Wien, Ixxiv, 1876, Siisswasserfische siiddstlicheu Bra- 

 siliens, iii, 40 (La Plata; Rio San Francisco; Rio das Velhas; 

 Amazon between Para and Santarem; Rio Grande do Sul; Porto 

 Alegre); Peters, MB. Ak. Berl. 470, 1877 (Calabozo). 



Pimelodus rigidus Spix, Gen. et Spec. Bras, plate vii, fig. 2, 1829. 



Pimelodus blochii Cuv. & Val. Hist. Nat. Poiss. xv, 188, 1840 (Cay- 

 enne; Surinam). 



Piramutana blochii Giinther, Cat. Fish. Brit. Mus. v, 111, 1864 

 (copied); Vaillant, Bull. Soc. Philom. series 7, iv, 152 (Cal- 

 deron). 



Pimelodus arekaima Schomburgk, Fish. Brit. Guiana, i, 178, plate 

 not descr. 1841 (Essequibo). 



Mystus ascita Gronow, "ed. Gray 156." 



Pseudorhamdia ascita Bleeker, " Versl. & Meded. Acad. Wet. 

 Amsterd. 1862, 384." 



Pimelodus macronema Bleeker, Sihires de Suriname, 79, plate 14, 

 1864 (Surinam). 



Pseudariodes albicans Liitken, Meddel. Nat. Hist. Foreu. 1874, Nos. 

 1 and 2, pages 194 and 198, not Arius, albicans of Valenciennes (La 

 Plata and its tributaries); Steiudachner, Fisch-Fauua Magda- 

 lenen Stromes 61, note, 1878. 



Pseudariodes pantherinus Liitken, Meddel. Nat. Hist. Forening. 

 1874, Nos. 1 and 2, pages 192 and 199 (Venezuela). 



Pseudorhamdia piscatrix Cope, Proc. Am. Philos. Soc. xi, 569, 1870 

 (Pebas); id. Proc. Philad. Acad. 1872, 262(Ambyiacu River); id. 

 Proc. Am. Philos. Soc. xvii, 674, 1878 (Peruvian Amazon). 



Piramutana macrospila Giiuther, Annals & Mag. Nat. Hist. July, 

 1880, 10, plate ii (Rio Plata). 



Habitat: Rio Plata and region to the north of it and east of the 

 Andes. 



There seems to have been considerable confusion in 

 the nomenclature of this species, owing to its great var- 

 iability, and for other reasons. 



Linnaeus had two species, this and one from the Nile. 

 Bloch figured the American species, while he gave as a 

 synonym the Nile species. His figure should restrict the 



