CHAPTER X. 



Subfamily LUTRINiE : The Otters. 



General considerations — Tlie genus Lidra — Generic characters and remarks— 

 Tiie North American Otter, Lufra canadensis — Synonymy — Habitat — 

 Specific characters— Description of external characters — Description of 

 the skull and teeth — Variation in the skull — History of the species — Geo- 

 graphical distribution — Habits of Otters — Extinct species of North Amer- 

 ican Otter. 



IN the Otters, we encounter a fourth decided modification of 

 the family characters in adaptation to a highly aquatic 

 mode of life. Among the true Mustelince^ indeed, we found 

 some aquatic species, like the Mink, Putorius viso7i; but in none 

 of the foregoing subfamilies is the structure modified to any 

 great extent with reference to natatorial abilities. The short, 

 broad, fully webbed feet of the Otters, the cylindrical body, the 

 stout tapering tail, and very turgid blunt muzzle result in an 

 unmistakable physiognomy, as characteristic of the Lutrinw as 

 are the more important structural modifications of the skull 

 and teeth. 



The Lutrlnce have been defined as Mustelidce with the number 

 of teeth equal in both jaws. This expression, however, is 

 equally applicable to the Unhydrlnce, or Sea Otter, in which, 

 very curiously, lack of one pair of under incisors brings about 

 the same adjustment of total teeth of the two jaws, though the 

 grinders are unequal in number. 



The Lutrince as here limited to the exclusion of Eahydrls may 

 be recognized as the only Mustelidce in which the number of 

 grinding teeth (molars and x>i'emolars together) is the same in 

 both jaws, the formula being i^w. ^^; m. ^ = JJ. The total 

 of the teeth is ^ = 36. The upper molar is large and quadrate 

 in shape. 



After throwing out the very different geuns Enhydrls as type 

 of a separate subfamily, the Lutrince still include a number of 

 well-marked genera. Of these, Lutra is the principal genus, 



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