Selachians Extraordinary 



265 





-^'^'•«> 





A South American Sting ray {Trygon nistrix). 



Courtesy, American Museum of Natural History 



are so well known that some Indian tribes tip their spears with the 

 stings of the rays, just as Pacific islanders do. 



Sting rays are similarly plentiful in the fresh waters of Thailand. 

 In his study of the fresh-water fishes of Thailand, pubUshed by the U.S. 

 National Museum in 1945, Hugh M. Smith reported a Sting ray, well 

 known in the Indian Ocean and the Indo-AustraUan Archipelago (Dasya- 

 tis sepheii), flourishing in fresh water. Though not strictly a River ray 

 (this ray does not anatomically qualify for membership in the Fotamot- 

 rygonidae family), Smith reported: "In the inner lake of the Tale Sap 

 it is quite common at times and produces young in the strictly fresh 

 waters of that 'inland sea.' " Another Thai Sting ray, identified by 

 Smith as D. bleekeri, is so acclimated to fresh water that it is called 

 pla kaheji inmj chiiet—'ihe. fresh-water rav fish." 



One species of River ray, known as the South American Fresh- Water 

 Sting ray {Potamotrygon vwtoro)^ is usually described by authorities 

 as an extremely dangerous species. It has been found in the fresh-water 



