140 



CLASSIFICATION OF FISHES. 



compressed. They all have an unequal tail, two dorsal 

 fins, and one anal. In the pre-eminently typical section, 

 or sub-genus, the tail is of ordinary length (Squalus 

 elephas Le Sueur, fig. 14.) ; but in the next sub-genus, 



Alopias Raf., to which the Squalus obscurus of Le Sueur 

 forms a passage, the upper division of the tail is exces- 

 sively lengthened; a familiar example of which is seen 

 in the fox-tailed, shark of Britain (Alopias vulpes Nob.).* 

 Independent of this singular development of tail, Alo- 

 pias is further distinguished by having the snout coni- 

 cal, not, as in. Squalus, broad and depressed; the teeth 

 also are less numerous, and are only in two or three 

 rows. The sub-genus Cericteus of Rafinesque is an 

 equally distinct, but a much more extraordinary, type, 

 hitherto found only on the prolific shores of Sicily t: it 

 is at once distinguished by having two horn-like osseous 

 appendages on the head, resembling horns ; while its 

 affinity to Alopias is manifested by its oblique, unequal, 

 but very long tail. All the foregoing types have an 

 anal fin, and the two dorsal fins are soft ; but in Dala- 

 tias nocturnus of Rafinesque, which he distinctly asserts 

 has no spiracle, the anal fin is wanting, and the two 

 dorsal fins are spinedv It has been thought by Cuvier, 

 that the spiracles of this fish have been overlooked, and 

 that it is, in reality, a species of Spinax; but we see no 

 good reason for this belief, and a strong one against 



* Figured in Yarrell, vol. ii. p. 379. 



t Cericteus macrourus, Raff. Caratt. p. 12. 



