THE ELASMOBRx\NCH FISHES 3 



eater," or greaX l)lue shark (fia:. 16) , and Cetorhinus, the basking shark (fig. 4) , 

 wliich not infrequently exceeds twenty-five feet in length. Finally, as an occa- 

 sional visitor np this coast may be added the giant of all fishes, Khinodon 

 fi/picus (fig. 3), specimens of which have been known to reach fifty feet in 

 length. 



To the above recent Elasmobranchs may be added the flattened sharks or 

 rays. Some of the most singular of these are Prist is the sawfish (fig. 19) with 

 nose prolonged into a two-edged saw, and Myliobatis the batfish (fig. 8) ; 

 Torpedo the electric ray (fig. 6) provided with a powerful battery by means 

 of which shocks of electricity may be administered to food or enemy alike; and 

 lastly, Cephaloptera, the giant of the ray tribe, growing in tropical seas to 

 more than a thousand pounds in weight and sometimes having a measurement 

 from tip to tip of pectorals exceeding twenty feet. 



Of the whole group of Elasmobranchs possibly none is of more interest than 

 the remaining notidanid sharks {Heptanchus and HexancMis) . Because of the 

 generalization found in these forms I propose in the following discussion of 

 the Elasmobranch fishes to use Heptanchus maculatus* (fig. 13) as a type with 

 which to compare in general other Elasmobranchs. 



* This shark is variously known as Notorhynclnis maculatus Ayres (1855), Heptanchus 

 maculatus Girard (1858), or Heptranchias maculatus Gill (1861). After making a detailed 

 study of this form and noting the marked differences between it and Heptanchus cinereus I 

 am almost persuaded that it merits the generic position ascribed to it by Ayers. Because of 

 the simple meaning of the word Heptanchus, however, and regardless of whether the etymol- 

 ogy of the word is or is not correct, I have retained the name given by Girard. 



