GEOGRAPHICAL DISTRIBUTION OF SEALS. 403 



definite forms and functions ranging from a large amount of 

 grinding surface in some mixed feeders, as Bears and Badgers ; 

 to teeth almost entirely formed for splitting bones and cutting 

 flesh, as in the Cats, &c. 



The Dolphins show a degradation, or reversion, towards the 

 older type of animals which had long narrow jaws, and rows of 

 similar conical teeth. 



Seals show some tendency in the same direction, inasmuch 

 as whilst their general cranial and dental aspect is unmistakably 

 canine or leonine, the teeth behind the canines approximate more 

 or less to this type of a series of cones. The teeth of various 

 genera and species differ a good deal, but they all agree in this, 

 that in each species all the teeth behind the canines are similar ; 

 there are not here as in the land Carnivora two or more distinct 

 sorts of teeth, — and where the species differ, they still keep up 

 the type of a series of recurved, more or less acute cones. 



A very early form of carnivorous tooth was perhaps taken as 

 the pattern of an old-fashioned spear-head, having a central sharp 

 blade supported on each side by two smaller cusps to help give 

 it grip and steadiness in action ; such teeth are quite common 

 in the land Carnivora, as anyone may judge by examining a cat 

 or dog. Such teeth are the basis of the pattern of the back- 

 teeth of Seals. 



Sometimes, as in Lobodon carcinophaga, a Seal from the 

 Antarctic Seas, there are three minor cusps behind the principal 

 one, as well as one in front, making five, whilst in others, as in 

 our own Halicharus grypus, the inferior cusps are reduced to a 

 mere indication, and the teeth have all nearly arrived at the 

 degradation of a merely conical type. Still in each case all the 

 teeth behind the canines are similar. 



Pinnipeds include the Eared Seals (Otariithc), the "Sea 

 Lions," and Fur Seals : the Walruses {Odonlxenidce) and the 

 ear-less or true Seals (Phocidce) comprising the Common Seals, 

 the "Sea Leopards" of the South Pacific, and the "Sea 

 Elephants." It has often been suggested that an affinity 

 between the Walrus and the Dugong is indicated by the tusks 

 of the latter ; but the relationship is only superficial, the tusks 

 of the Dugong being enlarged incisors, while those of the Walrus 

 are the canines. The Dugong is a true vegetable-feeder, whilst 

 the Walrus — in spite of a recent writer in the ' Century ' 



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