ICHTHYOLOGY OF VENEZUELA — SCHULTZ 27 



Genus POTAMOTRYGON Garman 



Potamotrygon Garman, Proc. Boston Soc. Nat. Hist., vol. 19, p. 210, 1877. (Geno- 

 type, Pastinaca humboldtii Roulin designated by Eigenmann, The fresh- 

 water fishes of British Guiana, p. 116, 1912.) 



Pastinaca Swainson (Natural history of fishes, amphibians . . ., 

 vol. 1, p. 172, 1838), is not a synonym of the genus Potamotrygon 

 Garman, as Swainson says: "Pastinaca Antiq. differs from Try g on 

 only in having the tail entirely naked: the common sting ray of the 

 Mediterranean is the type of this genus, to which we prefer retaining 

 the name by which it was known to the ancients." Pastinacae 

 Nardo, Giorn. Fisica de Pa via, vol. 1, p. 11, 1827, with genotype Raja 

 pastinaca Linnaeus, is an older name according to Jordan (Genera 

 of fishes, pt. 1, p. 121, 1917). 



I have had for examination, in addition to the series listed from the 

 Maracaibo Basin, two specimens from the Orinoco system, two from 

 the Kio Ampiyacu of the Peruvian Amazon, and one from the Rio 

 Magdalena. On these I have based my key. Because of the vari- 

 ability in body proportions I considered it advisable not to use the 

 measurements. The coloration is so strikingly different for the 

 specimens from the three drainage basins that I am able to dis- 

 tinguish the three species at a glance. The presence or absence of 

 white blotches or black spots on the dorsal surface was so variable 

 for the large series of specimens from the Maracaibo Basin that I 

 cast serious doubt on those characters as of value in distinguishing 

 the species referable to the genus Potamotrygon. 



For detailed measurements made on specimens of Potamotrygon, 

 see table 2. 



POTAMOTRYGON HUMBOLDTH (DumgrU) 



Stingray; Rata de agua DUiiCE 



Pastenaque Humboldt, Roulin, Ann. Sci. Nat., vol. 16, pp. 104-107, pi. 3, figs. 

 1-3, 1829 (Upper Rio INIeta, Province San Martin at Giramena). (No 

 binomial name given.) 



Pastin[aca] humboldtii, Roulin, in Dum^ril, Histoire naturelle des poissons ou 

 ichthyologie g^n^rale, vol. 1, p. 625, 1865. 



Taeniura d'orbignyi Steindachner, Denkschr. Akad. Wiss. Wien, vol. 41, p. 

 159, 1879 (Ciudad Bolivar). 



Trygon hystrix Peters, Monatsb. Akad. Wiss. Berlin, 1877, p. 473 (Apure, 

 Venezuela). — Sachs, Aus dem Llanos, 1879, p. 146 (Apure). — Rohl, Fauna 

 descriptiva de Venezuela, p. 368, fig. 181, 1942 (Orinoco). 



Potamotrygon hystrix Eigenmann and Eigenmann, Proc. U. S. Nat. Mus., vol. 

 14, p. 25, 1891 (Apure; Orinoco).— (in part) Fowler, Mus. Hist. Nat. Lima, 

 1945, p. 19 (Venezuela). 



Potamotrygon d'orbignyi (in part) Eigenmann and Eigenmann, Proc. U. S. 

 Nat. Mus., vol. 14, p. 25, 1891 (Orinoco, near Ciudad Bolivar).— Eigen- 

 mann, Reports Princeton Univ. Exped. Patagonia 1896-1899, vol. 3, pt. 4, 

 p. 378, 1910 (Apure of Orinoco). 



