l60 CLASSIFICATION OP FISHES. 



ferent ; that is, the rays would be a typical^ and the 

 birds a sub-typicalj group. This latter denomination, as 

 applied to the class Aves, is so unquestionable^ that it 

 must remain undisturbed. Analogy must always be 

 made subservient to affinity ; and as this very transport- 

 ation of the two typical groups has been frequently 

 observed in ornithology, we must leave it to time, and 

 a better acquaintance with the theory of variation, to 

 clear up a question so beset with difficulties. 



(142.) The analogies of the two first groups in each 

 of these columns are, of course, only applicable to the 

 typical examples of each ; while the only exception to 

 the whole of the Squalince being destitute of spines, 

 rests on the question whether the Dalatias nocturnus 

 of Rafinesque has been correctly described as without 

 spiracles : should this really be an error, then this sup- 

 posed genus must be abohshed, and the above-named 

 fish will become, as Cuvier conjectures, a species belong- 

 ing to the CentrincB. This question, however, is of no 

 importance to our present purpose, for we are looking to 

 lai"ge assemblages, not to the pecuharities of the sub- 

 genera : besides, it is quite clear that, even if some of 

 the sharks without spiracles have spinous fins, the 

 greater portion have not ; while, as the majority 

 of those with spiracles also possess spines, this latter 

 character becomes one of their typical distinctions. In 

 this manner, the Centrince will, of course, represent the 

 rays. Now, the nearest approach which is made by the 

 sharks to the saw-fish, seems to beby the gQrm.'s. Mustelus, 

 because it has, like Pristis and the rays, tesselated teeth ; 

 hence we have supposed that they are united by affinity, 

 although there appears an hiatus between Mustelus and 

 Pristis, which nothing yet known is calculated to fill 

 up. "Whether we are correct in this supposition, time 

 only will show. The aLnalogy oi Pristis to the Chimcerin^ 

 is manifested by the tooth-like processes of their snouts; 

 those in Pristis assuming the form of teeth, those of 

 Chimcpra prickles. It might be thought, indeed, that 

 Pristis was more analogous to Polyodon, because the 



