THE 



SECOND ORDER OF CHONDROPTERYGII, 

 AND EIGHTH OF FISHES, 



OR 



CHONDROPTERYGII WITH FIXED BRANCHLE. 



Instead of having the gills free at the external edge, 

 and opening at their intervals into a wide common 

 foss, as in all the fishes of whi^h we have spoken 

 hitherto, these have them, on the contrary, adherent 

 by this external edge, so that they suffer the water to 

 escape by as many holes pierced in the skin as there 

 are intervals between them, or at least those holes 

 terminate in a common conduit, which transmits the 

 water to the outside. Another circumstance peculiar 

 to these fishes, consists in having small cartilaginous 

 arches, often suspended in the flesh, opposite the 

 exterior edge of the gills, and which may be called 

 branchial ribs. 



The Qhondropterygii with fixed gills of the first 

 family, or the 



Selacii, (Plagiostomi, Desm.) 



Hitherto comprehended under two genera, Squalus 

 and Rata, have many characters in common. 



