POTAMOTRYGON ORBICULARIS. 123 



POTAMOTRYGON MOTORO. 



'I\i, ni urn nullum Mi \.\.v.m & Henle, Isll, Plagios., p. L97; Di'Mioiiii., 1865, Blasm , p. 624; Gunth., 



INTO, Cat. Bshes Brit, mus., 8, p. 184. 

 Trygon garrapa Schomburgk, L843, Fishes Guiana, 2. p. 182, pi. 21; Muller A- Troschel, 1848, 



Schomburgk's reisen, 3, p. 642. 

 Trygon {Taenura) dumerttii Castelnau, 1855, Anim. nouv., Poiss., p. 101, pi. is, f. l. 

 Trygon (Taenura) mutteri Castelnau, L855, ibid., pi. is, f. 2. 

 Trygon [Taenura) henlei Castelnau, 1855, ibid., pi. 48, f. 3. 

 Potamolrygon motoro Gasman, 1877, Proc. Bost. soc. nat. hist., 19, p. 211; Eiuenmann, 1892, Pnic 



U. S. nat. mus., 15, p. 25. 

 Ellipesurus motoro Ribiero, 1907, Arch. Mus. uac, 14, p. 1S5. 



Disk oval almost round. Mouth with five papillae; teeth flat. Upper 

 eyelid slightly produced in the middle. Back rough, except at the edges, with 

 stellate-based spines, stronger near the vertebral column on disk and tail. 

 Base of tail with a row of compressed round-based spines which extends forward 

 with age on the hinder part of the back; sides of tail rough to the end. Tail 

 as long as the disk, with a serrated spine remote from the body, and with a 

 cutaneous fold above and another below. 



Brown with numerous round spots of yellow to orange, more often ocellated 

 by black edges, on back and tail, fainter near the margins below the disk and 

 under the tail. 



Originally described from the Cuyaba, apparently found in both the Plata 

 and the Amazon systems. Muller and Henle appear to have had some doubts 

 in regard to the differences between this species and P. hystrix. 



POTAMOTRYGON ORBICULARIS. 



.'Aicrcba Marcgrave, 1648, Hist. nat. Brasil., p. 175, fig.; Jonst., 1649, Pise, pi. 38, f. 6; Willughby, 



1686, Pise, p. 48, pi. CI, f. 2. 

 Raia orbicularis Schneider, 1801, Bloch Ichth., p. 361. 

 Trygon aicrcba Muller & Henle, 1841, Plagios., p. 160. 

 Trygon (Paralrygon) aiereba Dumeril, 1865, Elasm., p. 594 (part). 

 Trygon orbicularis Gunth., 1870, Cat. fishes Brit, mus., 8, p. 482 (part). 



Disk as wide as long, spiracles nearly one fifth of the length of the disk 

 from the front margin; about one seventh of the same length equals their 

 distance apart. "Os inferius habet, haud amplum, edentulum; incisurae quasi 

 parabolicae." Tail slender, more than twice as long as the body, with two spines 

 near the middle of its length. Length of disk and width equal, 21 inches each; 

 length of tail four feet. 



Back reddish, covered in the middle with small tubercles; lower surfaces 

 white. 



A doubtful species, known only from Alarcgrave's description. 



