Selachians Extraordinary 273 



Pacific Eagle ray's appetite for oysters has inspired the erection of sea- 

 bottom fences by Pacific oystermen. These fences are made by driving 

 stakes about 6 inches apart so that the wide-winged rays cannot squeeze 

 through. These hungry rays, equipped with pavement-Hke teeth well 

 suited for crushing oyster shells, also attack clam beds. Lionel A. Wal- 

 ford, of the U.S. Fish and Wildlife Service, reporting on the Eagle ray's 

 clam-digging technique, said that it "swims along the bottom until it 

 meets the currents of water expelled by the siphons of clams. It then 

 flaps its pectoral fins, creating a suction which digs out the clams. Some- 

 times it fiaps along in this manner for considerable distances, leaving 

 behind a barren trough." 



Though Eagle rays are commonly not believed to be abundant along 

 the Atlantic or the Pacific coasts of America, schools of several thou- 

 sand have been reported at times in the waters of Lower California. 



Studies of the embryo of M. calijornicus have solved the puzzle of 

 how female Sting rays bring forth their sting-bearing young without 

 being stung themselves. The pup's sting is pliable and covered with a 

 sheath that is sloughed off soon after birth, so that, like all other Sela- 

 chians, the newborn Eagle ray is immediately ready to defend itself. 



The venom-bearing Duck-Billed rays are also included in the Mylio- 

 batidae family. The Spotted Duck-Billed ray {Aetobatiis narinari Eu- 

 phrasen, 1790), a big, speckled creature, is found not only on both sides 

 of the Atlantic, but also in the Pacific and the Indian Oceans, and the Red 



Spotted Duck-billed ray (Aetohatus narinari). 



Courtesy, Miami Seaqiiarium 



