6 8 Memoir Sears Foundation for Marine Research 



4 (3), 1913: loi (range); Garman, Mem. Harv. Mus. comp. Zool., j6, 1913: 279, pi. 17 (descr., 

 ill., Florida); Gudger, Proc. biol. Soc. Wash., 26, 191 3: 98 (listed, Beaufort, N. Carolina); Coles, Proc. 

 biol. Soc. Wash., 28, 1915: 92 (nos., size, season, C. Lookout, N. Carolina); Radcliffe, Bull. U. S. Bur. 

 Fish., 34, 1916: 269 (descr., ill., teeth, denticles, C. Lookout, N. Carolina); Barbour, Copeia, 85, 1920: 

 71 (habits. Palm Beach, Florida); Meek and Hildebrand, Field Mus. Publ. Zool., 25 (i), 1923: 70 

 (color, cf. R.percellens, not recorded for Atlant. Panama); Norman, Proc. zool. Soc. Lond., 1926: 947 

 (in Key), 969 (descr., ill., Morehead City, N.Carolina); Breder, Field Bk. Mar. Fish. Atlant. Coast, 

 1929: 28 (genl.); Jordan, Manual Vert. Anim. NE U. S., 1929: 16 (diagn., N. Carolina south); Jordan, 

 Evermann and Clark, Rep. U. S. Comm. Fish. (1928), 2, 1930: 23 (listed, Charleston, S. Carolina- 

 Yucatan); Bere, Amer. Midi. Nat., l"], 1936: 582 (parasites. Lemon Bay, Florida); Fowler, Monogr. 

 Acad. nat. Sci. Philad., 7, 1945: 98, 160 (listed, N. and S. Carolina). 



Rhinobatos percellens (Walbaum) 1792 



Southern Guitarfish 



Figures 1 2 C, 16 



Study Material. Nineteen specimens, male and female, 210 to 591 mm long, in 

 Harvard Museum of Comparative Zoology and U. S. National Museum, from Santos, 

 Rio de Janeiro and Pernambuco, Brazil; Colon, Panama; and Jamaica. 



Distinctive Characters. Rhinobatos percellens closely resembles both R. lentiginosus 

 and R. horkelii in general form and in most of its proportionate dimensions. It is dis- 

 tinguishable from horkelii by its somewhat shorter nostrils; also by the facts that its 

 crown is definitely, though only slightly, concave transversely, and that its tubercles 

 along the midline of the back are smaller and less thorn-like in form. It differs from 

 R. lentiginosus^^ chiefly in that there are no enlarged tubercles on the tip of the snout 

 in typical specimens (several such tubercles in R. lentiginosus)\ on specimens oi per- 

 cellens that are white-spotted, the spots are not only much less numerous than on most 

 specimens of R. lentiginosus but are symmetrically arranged on either side of the median 

 line; and the rostral cartilage is narrower in percellens than in lentiginosus., especially 

 toward the tip. We have seen three specimens intermediate between the two species: 

 one from Texas, which has tubercles on its snout (as in R. lentiginosus) but has no 

 white spots (p. 65), and two from Jamaica, sparsely white-spotted (as in R. percellens) 

 but with a pair of somewhat enlarged tubercles side by side on the tip of the snout 

 (as in R. lentiginosus). 



Description. Proportional dimensions in per cent ot total length. Male, 557 mm 

 (Harv. Mus. Comp. Zool., No. 435) and female, 591 mm (Harv. Mus. Comp. Zool., 

 No. 542) from Rio de Janeiro, Brazil. 



Disc: extreme breadth 30.5, 32.3; length 38.8, 40.0. 



Snout length: in front of orbits 14.7, 14-7; in front of mouth 16.7, 17.1. 



Orbits: horizontal diameter 3.6, 3.4; distance between 3.2, 3.1. 



Spiracles: length 2.2, 2.3; distance between 5.0, 5.2. 



Mouth: breadth 6.3, 6.5. 



Nostrils: length 3.7, 3.2; distance between inner ends 3.1, 3.4. 



59. Perhaps the only significant differences that can be relied upon. 



