162 CLASSIFICATION OF FISHES. 



their internal analogies. Some of the more recently cha- 

 racterised forms we have not personally examined, and 

 others are not now before us, so that we had almost de- 

 termined not to have prosecuted our analogical views 

 further than to the sub-families : but this might have 

 given an impression to some few of our naturalists, that 

 the theory could not be carried further, and that we de- 

 serted our former declaration, that every group, whether 

 ]arge or small, if natural, would contain representations 

 of all others. To show, therefore, that, even in our 

 present dilemma, there is some ground for this asser- 

 tion — so fully demonstrated already in the class of 

 birds — we shall make the attempt. If one or two of 

 these analogies carry with them an appearance of truth, 

 our principle, substantially, is gained ; while, for the 

 rest, if we are in error, these very errors will serve as 

 land-marks to others, and elicit that additional inform- 

 ation which is absolutely essential before we can hope to 

 work out the internal affinities and analogies of the great 

 number of forms comprised in the sub-families Squalince 

 and CentrincB. 



Analogies of the Squalix^e and the Centring. 



Genera of the -r, • . • *■ _? ? • i Genera of the 



Sqcalinx ; Bistinct>ve and analogical Centring; 



no spiracle! Characters. with spiracle^. 



Squalus Linn. Typical of their respective groups. Centrina Cuv. 



Dalatias Raf. Spines to the dorsal ; no ventral fin. Galeus Raf. 



t t> r ("Snout or muzzle excessively long, 7 c ;>• ™ r-. 



IsurusIteZ J projecting beyond the mouth. *$ ScffBium Cuv. 



Rineodon Smith P^S vertical.'^ ° f themUZzle: } Cestracion Cuv. 



f The second dorsal fin opposite the") ■ 

 anal : the two last branchial j 

 Scoliodon M. H. < openings placed above the pecto- yMustelus Cuv. 



rai fin : teeth the same in both 



L jaws. 



(14-i.) It will tend much to elucidate the above table, 

 if we first of all briefly recapitulate the reasons that have 

 induced us to arrange these two series in the order in 

 which thev now stand; so that, before entering on an 

 explanation of the analogies they bear to each other, we 

 shall take a hastv glance at the affinities of the srenera 



