184 VERTEBRATA. PISCES. 



ORDER II. PECTOBRANCHIATL* 



THESE differ from all other fishes, in not having 

 the gills free on their outer edge, and opening all 

 their intervals into a single large orifice, but adhering 

 by that edge, so as to permit the water to escape 

 through just so many apertures as there are intervals, 

 or at least so that these holes terminate in a common 

 aperture through which the water is sent. 



FAM. I. SELACHII.f 



The true bones of the jaws are wanting, but their 

 place is supplied by the bones of the palate, and 

 some others which are armed with teeth. The ven- 

 trals are placed behind the abdomen, on each side 

 the vent : in the males, these fins have long appen- 

 dages, the use of which is not ascertained. The- 

 females in some cases bring forth living young; in 

 others, the young are produced enclosed in leathery 

 cases, or sacs. This family is composed of two 

 large groups, the Sharks and the Rays. 



* nj*Taf, pektos, fixed, and figK>y%iet, branched, gills. 



f 2eX^aj, selachos, the Greek name of the cartilaginous fishes. 



