142 FOOD OF THE WALEUS. 



the shells Tridacnse and Cardia, vulgarly called 

 clams and cockles : I believe they also eat 

 submarine algae or seaweeds, and Scoresby 

 mentions having found the remains of young 

 seals in their stomachs ; but I imagine the 

 latter case to be an unusual one, as the seal is 

 a much more active animal in the water than 

 the walrus, and I have never met with any one 

 else who had observed it. 



The tusks of the walrus are not an extra 

 pair of teeth, but simply an enlargement and 

 modification of the eyeteeth, produced, as I 

 believe, by the necessity the animal has for 

 long tusks, in order to obtain his food in the 

 way he does. 



They are very firmly and strongly embedded 

 for about six or seven inches of their length in 

 a mass of very hard and solid bone, forming 

 the front of the animal's head ; this bony pro- 

 tuberance is the size of a man's skull, and 

 through it runs the passage by which the 

 walrus breathes, the blow holes lying between 

 the roots of the tusks. The part of the tusks 

 which is embedded in the head is hollow, but 

 is mostly filled up with a cellular bony sub- 

 stance containing much oil; the remainder 

 of the tusk is hard and solid throughout. 



