36 THE PORBEAGLE SHARK; NOTIDANID.E ; CESTRACIONTID.-E. 



Porbeagle Shark is about eight or nine feet in length, and is 

 not uncommon in the British seas. Its English name seems to 

 be compounded of Porpoise and Beagle ; for it bears some re- 

 semblance to the former in shape, whilst it corresponds with the 

 latter in its habit of hunting in packs. It is voracious in its 

 habits, swallowing entire Fishes of two feet in length. The 

 Basking Shark, which is also found in our seas, is a much larger 

 species, and indeed is the largest of existing fishes, measuring 

 sometimes no less than thirty-six feet in length. It is, however, 

 by no means ferocious in its habits, and appears to feed principally 

 upon small marine animals. It receives its name of Basking 

 Shark, and also that of Sun-fish, which is applied to it in some 

 localities, from its habit of floating at the surface of the water in 

 calm warm days. Its branchial apertures are very large. The 

 NOTIDANID^E, which are closely allied to the Lamnidse, have only 

 a single dorsal fin, and their branchial apertures are six or seven 

 in number. Two species are found in the Mediterranean ; none 

 of them seem greatly to exceed three feet in length. The CES- 

 TRACIONTID^E, of which only a single existing species is known, 

 although the remains of extinct forms are very abundant in some 



WHITE SHARK. 



of the earlier formations, have pavement-like teeth ; the front 

 teeth are pointed, whilst the hinder ones are converted into regu- 



