146 CLASSIFICATION OF FISHES. 



Cuvier observes, has all the characters of Scymnus, but 

 with the addition of spines. The most common ex- 

 ample of this type is the Squalus centrina of Linnaeus, 

 — a large, thick-shaped fish, having the spines not placed 

 in front of the dorsal fins, but partly concealed in the 

 skin which covers them : the anterior spine points for- 

 ward, but the posterior is directed -^ backward, and the 

 tips of both are alone naked : the last dorsal fin is 

 placed over the ventral ; and the tail is remarkably 

 short. We exclude from this sub-genus the Squalus 

 spinosus and squamosus of authors, the last of which 

 appears to us the true type of the sub-genus CentrophO' 

 rus of Muller and Henle, the distinctive and most 

 striking characteristic of which is the body being covered 

 with hard carinated scales. The sub-genus Somnolentus 

 of Le Sueur seems to unite this singular form with 

 Scymnus, of which we consider it only as an aberrant 

 species. The fourth sub- genus, following Centrina, is 

 Spinax Cuv. *, where we have again the ordinary form 

 of the sharks, but with each of the dorsal spines placed 

 in front of the fins : the snout is rather lengthened, the 

 tail long and unequal, and the teeth are small and cutting. 

 The most familiar and typical example of this group is 

 the Spinax acanthias, or picked dog-fish of our own seas, 

 of which Mr. Couch has recently given us an interest- 

 ing account.? It seems to be the most abundant of all 

 the sharks found on the western coasts, w^here it is 

 sometimes seen in incalculable numbers, to the no small 

 annoyance of the fishermen, whose hooks they cut from 

 the lines in rapid succession. One of its modes of de- 

 fence is very singular, and is effected by bending itself 

 in the form of a bow, for the purpose of wounding 

 with its spines ; and then, by a sudden motion, it causes 

 them to spring asunder in opposite directions : so accu- 

 rately is this effected, that if a finger be placed on its 



♦ It appears to me that the sub-genus Acanthias Bonap. is the true type 

 of Spinax, and that the single one to which Cuvier's original name is 

 thus restricted, is but an aberrant species of Spincz. 



t Inserted in Yarrell's British Fishes, vol. ii. p. 401. 



