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PHYLUM CHORDATA 491 



In the Carnivora vera the typical number of digits is sometimes 

 present, or, more usually, there are five in the fore- and four in the 

 hind-foot, or four in each. The extremities of the digits are pro- 

 vided with compressed, curved claws, which may be very long and 

 sharp, when they are capable, when not in use, of being retracted 

 into a sheath of skin situated at their bases ; or relatively short 

 and blunt, when they are incompletely, or not at all, retractile. The 

 Dogs (Canidce) and Cats (Felidce) are digitigrade, the Bears ( Ursidce) 

 and allied groups plantigrade (p. 501). The Otters (Lutra) differ 

 from the rest in having short limbs with the toes connected by 

 webs of skin. 



The Pinnipedia (Fig. 1133) have the proximal segments of the 

 limbs short, so that the arm and thigh and nearly all the fore-arm 

 and leg are enclosed in the common integument of the trunk ; the 

 manus and pes are elongated. The Earless Seals (Phocidce) are 

 much more completely adapted to an aquatic life than the Eared 



FIG. 1133. Seal (Phoca vitulina). 



Seals (Otariidce) and Walruses (Trwhechidce), being unable to flex the 

 thigh forwards under the body so that the hind-limbs may aid in 

 supporting the weight, and thus being only able to drag themselves 

 along very awkwardly when on dry land. The pinna of the ear is 

 absent in the Earless Seals and Walruses, well developed in the 

 Eared Seals. The surface in all is covered with a thick, soft fur. 

 In the Fur-Seals there are two kinds of hairs those of the one 

 kind being longer and coarser, and scattered through the more 

 numerous shorter and finer hairs composing the fur proper. A 

 remarkable feature of the Walruses is the presence of a pair of 

 large tusks the enlarged canine teeth projecting downwards 

 from the upper jaw. 



Some of the Rodents (Beavers, Water- Voles) are aquatic, 

 some (Squirrels and Tree-Porcupines) are arboreal, while others 

 (the majority of the order) lead a terrestrial life, and are active 

 burrowers. They are on the whole a very uniform group, and 

 exhibit few such remarkable modifications as are to be observed in 

 some of the other orders of Mammals. They are nearly all furry 



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