422 FISHES. 



From the true sharks we come to the Hammerhead, one 

 of the most remarkable of living fishes, a rare visitor to 

 Hammer- British waters, but exceedingly numerous on 

 head. the other side of the world, where it is re- 



garded as one of the most dangerous ; and I know of 

 one man at least whose small boat was chased by one of 

 these brutes for over a mile up the Brisbane river until 

 in despair he ran her ashore. The most characteristic 

 part of this shark is the hammer-shaped head, the large 

 eye lying at either end and having a nictitating mem- 

 brane. Spiracles are absent. This fish grows to a length 

 of over 12 feet, and its colour is dark grey above, white 

 below. The upper lobe of the tail is twice as long as 

 the lower. This shark is viviparous, the young being 

 born in autumn. It is also known as the "Balance- fish." 



Another group of small ground-sharks is chiefly interest- 

 ing for the distinction existing before birth between the 

 Smooth two species that compose it. As some doubt 

 Hound, exists, indeed, as to whether the second of 

 these, Mustela Icevis, is to be regarded as a British fish, it 

 is convenient to consider the two under the same trivial 

 name of Smooth Hound. The difference alluded to is that 

 in this doubtful British subject which is, like its com- 

 moner congener, viviparous there is a placental connec- 

 tion between the unborn young and its parent, this con- 

 nection being absent in the other. The latter, which 

 is also known as the " Kay-mouthed Dog," is of frequent 

 occurrence on our coasts, examples of 4 feet being taken 

 on the ground-lines. In colour it is grey, with indistinct 

 white spots. The food of this species is said to consist 

 of crustaceans. 



The Porbeagle, the type of another group, belongs to a 



genus of which our seas contain no other 

 Porbeagle. mi 



member. I he fins are spineless as in the fore- 

 going, but the eye has no nictitating membrane, and the 



