CHONDROPTERYGII BRANCHIIS LIBERIS. 237 



apparent hole on each side, although if we penetrate more deeply, we 

 find that they are attached by a large part of their edges, and that in fact 

 there are five particular holes terminating 1 in the bottom of the common 

 aperture. A vestige of an operculum, however, is concealed under the 

 skin. The jaws are still more reduced than in the Shark, for the palatine 

 and tympanic bones are also mere vestiges suspended to the sides of the 

 snout, and the vonier is the only representative of the upper jaw. Hard 

 and indivisible plates supply the place of teeth, four on the upper jaw and 

 two on the lower. The snout, supported like that of a Shark, projects 

 forwards and is pierced with pores arranged in tolerably regular lines; the 

 first dorsal, armed with a strong spine, is placed over the pectorals. They 

 produce very large coriaceous eggs with flattened and hairy borders. 



C. monstrosa, L. (The Arctic Chimaera.) Two or three feet long, of a 

 silvery colour, and spotted with brown. From the Northern and Euro- 

 pean seas. 



ORDER II. 

 CHONDROPTERYGII BRANCHIIS FIXIS, 



Or the Chondropterygii with fixed branchise, instead of having 

 those organs free on the external edge, and opening all their inter- 

 vals into a large common orifice, as is the case in all the fishes of 

 which we have hitherto spoken, have them adhering by this external 

 edge in such a manner that they permit the water to escape through 

 as many holes pierced in the skin as there are intervals between 

 them, or, at least, that these holes may terminate in a common duct, 

 through which the. water is ejected. Another circumstance pecu- 

 liar to these fishes is the presence of little cartilaginous bows, fre- 

 quently suspended in the muscles opposite to the external edges of 

 the branchiae, and which may be termed branchial ribs. 



FAMILY I. 

 SELACHII. 



This family, hitherto comprized under two genera, SQTTALUS and 

 RAIA, has many common characters. The palatines and post-man- 

 dibularies, alone armed with teeth, supply the place of jaws, the 

 usual bones of which are reduced to mere vestiges; one single bone 

 suspends these apparent jaws to the cranium, representing at once 



