320 FISHES. 



from teetli only, have been considered generically distinct 

 from the living Porbeagles. 



Lamna (Oxyrhina). — The second dorsal and anal are very small. 

 A pit at the root of tlie caudal, which has the lower lobe much 

 developed. Side of the tail with a prominent 

 longitudinal keel. Mouth wide. Teeth large, 

 lanceolate, not serrated, sometimes with addi- 

 tional basal cusps. On each side of the upper 

 Fig. 113.— Upper and jaw, at some distance from the symphysis, there 

 lower tooth of Lamna. -g ^^^^ ^j. ^^^^ ^^^^^i conspicuously smaller 



than the others. Gill-openings very wide. Spiracles minute. 



Of the " Porbeagles," three species have been described, 

 of which the one occurring in the North Atlantic, and fre- 

 quently straying to the British coasts (Z. cornuhica), is best 

 known. It attains to a length of ten feet, and feeds chiefly 

 on fishes ; its lanceolate teeth are not adapted for cutting, 

 but rather for seizing and holding its prey, which it appears 

 to swallow whole. According to Pennant it is viviparous ; 

 only two embryoes were found in the female which came 

 under his ol)servation. Haast has found this species also off 

 the coast of New Zealand. 



Carcharodon. — The second dorsal and anal are very small. 

 Pit at the root of the caudal, which has the lower lobe well de- 

 veloped. Side of the tail with a prominent longitudinal keel. 

 Mouth wide. Teeth large, flat, erect, regularly triangular, ser- 

 rated. On each side of the upper jaw, at some distance from the 

 symphysis, there is one or two teeth conspicuously smaller than 

 the others. Gill-openings wide. 



One species only is kno^vn (C. rondcldii), which is the 

 most formidable of all Sharks. It is strictly pelagic ; and 

 appears to occur in all tropical and sub- tropical seas. It 

 is known to attain to a length of 40 feet. The tooth figured 

 here, of the natural size, is taken from a jaw 20 inches wide 

 in its transverse diameter (inside measure), each half of the 



