154 Mejnoir Sears Foundation for Marine Research 



■platana Giinther 1880. 

 Rio de Janeiro'^ and mouth 

 of La Plata River. 

 2 b. Lower surface of disc not marked with black dots or streaks. 



6 a. No large thorns anywhere on disc anterior to level of axils of pectorals. 

 7 a. Distance from cloaca to tip of tail shorter than that from cloaca to 

 tip of snout; outer posterior parts of pectorals mostly smooth. 



scaphiops Norman 1937. 

 North of Falkland Islands. 



7 b. Distance from cloaca to tip of tail longer than distance from cloaca 



to tip of snout; outer posterior parts of pectorals with extensive 

 prickly areas. griseocauda Norman 1937. 



Patagonian-Falklands region. 

 6 b. Disc anterior to level of axils of pectorals with conspicuous thorns either 

 along midline, around orbits, on scapular regions, or on all three parts. 



8 a. No thorns on scapular regions. 



9 a. Tail with only one row of thorns. 



loa. Snout in front of orbits at least four times as long as 

 distance between orbits; anterior margins of disc deeply 

 concave. echinorhyncha Ribeiro 1923. 



Rio de Janeiro, 

 lob. Snout in front of orbits not more than 2.5 times as long 

 as distance between orbits; anterior margins of disc not 

 deeply concave. 



1 1 a. Disc with many small rounded white spots; thorns 

 on tail noticeably larger than those along mid-dorsal 

 line on disc. albomaculata Norman 1937. 



Patagonian-Falklands region. 

 lib. Disc not marked with many small white spots; 

 thorns on tail not larger than those on midline of disc. 

 brachyurops Fowler 19 10. 

 Northern Argentina (.'); Pata- 

 gonian-Falklands region. 

 9 b. Tail with two lateral rows of thorns along each side in addition 

 to median row. brasiliensis M tiller and Henle 1841. 



Brazil. 

 8 b. Each scapular region with 1—3 thorns. 



12 a. Only 12 — 15 thorns along midline of back and tail trom nuchal 

 region to first dorsal fin, all large. 



doello-juradoi Pozzi 1935. 

 Northern Argentina to Patago- 

 nian-Falklands region. 



65. On re-examination, the specimen from Rio de Janeiro described by Garman (Mem. Harv. Mus. comp. Zool., 

 36, 191 3: 361) under the name R. castelnaui Ribeiro 1904 proves not to be that species; it agrees closely with Gunther's 

 account and illustration (Challenger Rep., Zool., i [6], 1880: 11, pi. 3) of R. platana. 



