3 9^ Memoir Sears Foundation for Marine Research 



Developmental Stages. The Butterfly Rays are ovoviviparous; for a further account 

 of Development, see p. 397. 



Habits. Their method of swimming, their habits, and their diet are essentially 

 similar to those of the long-tailed Sting Rays (Dasyatidae), but little detail is known of 

 their way of life. 



Relation to Man. None are of any commercial importance anywhere. Obviously, 

 such of them as lack a tail spine are perfectly harmless. Even those that are armed with 

 a spine (or spines) are much less dangerous than are the long-tailed Rays, their tails 

 being much smaller and hence less effective as weapons. 



Range. Cosmopolitan in tropical to warm-temperate latitudes, in shallow coastal 

 waters, including estuaries and river mouths. 



Genera. The known species of the family fall into two groups, according to whether 

 or not a dorsal fin is present. While the demarcation between the two may not be as 

 sharp as the taxonomist might wish, we follow Garman^ in recognizing two genera, 

 Aetoplatea (without fin) and Gymnura (with fin). 



Key to Genera 



I a. A small but distinct dorsal fin near midlength of tail. 



Aetoplatea Mtiller and Henle 1841. 



South Africa, Red Sea, Indian Ocean, East 



Indies. 

 lb. No dorsal fin; at most a low longitudinal keel on upper surface of tail. 



Gymnura van Hasselt 1823,^ p. 396. 



Genus Gymnura van Hasselt 1823 



Gymnura van Hasselt, Allg. Konst. en Letterbode Haarlem, 1823: 316; Bull. Univ. Sci. Nat., 2, 1824: 90; 

 type species, Raja micrura Bloch and Schneider 1801; Surinam (Dutch Guiana).* 



Generic Synonyms: 



Raja (in part) Linnaeus, Syst. Nat., j, 1758: 232; for R. altavela Linnaeus. 



Trygonobatus (in part) Blainville, Bull. Soc. philom. Paris, 18 16: 112; for T. aitavelus and T.microurus Blain- 



ville, which no doubt equal Raja altavela Linnaeus 1758 and Raja micrura Bloch and Schneider 1801. 

 Trygon (in part) Cuvier, Regne Anim., 2nd ed., 2, 1829: 400, footnote; for T.kunsua Cuvier (based on the 



Tenkee Kunsul of Russell, Fish. Coromandel, j, 1803: 4, pi. 6); Raja micrura Bloch and Schneider 



1 80 1 and Raja maclura Lesueur 18 17 also included. 



2. Mem. Harv. Mus. comp. Zool., j6, 1913: 373, 411, 412. Fowler (Bull. U. S. nat. Mus., 100 [jj], 1941: 450) reduces 

 Aetoplatea and Pleroplatea to subgeneric rank under Gymnura. 



3. The generic name Gymnura was published first by van Hasselt (AUg. Konst. en Letterbode Haarlem, 1823: 316 

 [not seen]; Bull. Univ. Sci. Nat., 2, 1824: 90) from a manuscript by Kuhl. Miiller and Henle later (S.B. Akad. 

 Wiss. Berl., 1S37: 117) used Gymnura for another genus of Rays, but these authors subsequently recognized that it 

 was preoccupied (Arch. Naturg., j, 1837: 437); they therefore proposed Urogymnus as a substitute for their Gymnura. 

 Gymnura was revived for the Butterfly Rays by Rey (Fauna Iberica, Feces, i, 1928: 635, and footnote) and by 

 Fowler (Proc. Acad. nat. Sci. Philad., 55, 1934: 241)- I' antedates and therefore supersedes Pteroplatea Muller and 

 Henle 1841. 



4. Fowler (Bull. U.S. nat. Mus., 100 [/j], 1941: 355) characterizes the locality as "likely erroneous" but without 

 further comment. 



