Fishes of the IVestern North Atlantic 330 



are objects of concern to fishermen and to anyone else wading in the shallow water in 

 regions where they are likely to be encountered, because wounds by their tail spines are 

 followed almost immediately by excruciating pain,^^ by severe swelling, by violent 

 muscular cramps, and often by subsequent inflammation and gangrene. Even fatalities 

 have been reliably recorded. ^^ Ordinarily recovery follows without any serious com- 

 plications, but in any case the mechanical damage to tissues incident on the extraction 

 of the spine is likely to be considerable because of its many-barbed structure. 



Range and Bathymetric Distribution. The Whip-tailed Sting Rays are primarily a 

 warmwater group; many of them are confined strictly to tropical-subtropical latitudes 

 the year round; some are resident along warm-temperate coasts, and others carry out 

 more or less regular and extensive migrations to higher latitudes with the vernal rise 

 in sea temperatures, withdrawing again to warmer waters with autumnal cooling. Most 

 of the Sting Rays are confined to shallow coastwise waters; in many parts of the world 

 they commonly follow the rising tide onto mud- and sand-flats to retreat again on the 

 ebb. Some occur commonly in the shoal channels and lagoons among the mangroves 

 on tropical coasts, and some run up into fresh water. But others are known to occur 

 as deep as 20-60 fathoms, possibly deeper. -^ 



Genera. One member of the family is set apart so sharply from all others by its 

 lack of tail spines that recent students generally refer it to a separate genus, Urogymnus 

 Muller and Henle 1837. A second group, consisting of a few species that are charac- 

 terized by the possession of a broad fold extending along the lower surface of the tail 

 to the tip, constitutes a second well marked genus, Taeniura Muller and Henle 1837. 

 A separate genus, Urolophoides Soldatov and Lindberg 1930, seems also needed pro- 

 visionally for an East Asian Ray that has a tail spine, an upper caudal fold but seemingly 

 no lower caudal fold, and a tail much shorter than the disc; unless, indeed, the unique 

 specimen that served as the basis for the description had been mutilated (see p. 340, 

 footnote 29). Opinions have diff"ered, however, as to whether the 30 or more remaining 

 members of the family, with long whiplash tails armed with spines and with longi- 

 tudinal caudal folds (if any) terminating far short of the tip of the tail, are all referable 

 to a single genus or whether the differences in degree of development of caudal folds 

 and ridges deserve generic or subgeneric recognition. ^^ On the basis of our own ex- 



23. See Bassler (Science, ()6, 1942: 274) for a recent eye-witness account of the agonizing effects of a wound inflicted 

 on a man's foot by the tail spine of one of the closely allied River Rays [Potamotrygonidae) of the Amazon. 



24. Thus Schomburgk (Reisen Brit. Guiana, 1840-1844, 2, 1848: 37-38) wrote that during his stay in British Guiana 

 a laborer who was struck by a Sting Ray died in convulsions; Crevaux (Arch. Med. nav., 1882: 37), quoted by 

 Gudger (Bull. Hist. Med., 14, 1943: 478), reported that a companion on the Orinoco died in 1881 from a wound 

 by one of the river Rays; Vellard (Mem. Soc. zool. Fr., 29, 1932: 514-532) speaks of fatalities as sometimes occurring 

 from wounds by Sting Rays in Brazil. And Whitley (Fish. Aust., i, 1940: 198) quotes the case of a bather's death 

 following the direct penetration of the heart, almost certainly by a Sting Ray spine. 



25. Whitley (Fish. Aust., i, 1940: 201) states that the .-Australian Dasyatis bre'vicaudata is taken most often in 20-60 

 fathoms. 



26. Barnard (Ann. S. Afr. Mus., jj [i], 1925: 75) and Rey (Fauna Iberica, Feces, i, 1928: 620) refer all members 

 of this group to a single genus. On the other hand, Garman (Mem. Harv. Mus. comp. Zool., j6, 1913: 375) distribu- 

 ted them among four named "groups" within the genus Dasybatus, which Fowler (Bull. U. S. nat. Mus., 100 

 [/j], 1941: 403) ranks as subgenera of the genus Dasyatis. However, Jordan, Evermann and Clark (Rep. U. S. 

 Comm. Fish. [1928], 2, 1930: 21) dignify the three groups that they mention [Paslinachus, Dasyatis, Amphotistius) 



