QUAD11UPEDS. 187 



a. With the three kinds of grinders. 



57. LUTKA. Otter. Six incisors on each jaw. Tail 

 nearly the length of the body. Two anal scent-bags. 

 Lutra mdgaris. 



58. ENHYDRA. Sea Otter. Six incisors above, and 

 four below. Tail much shorter than the body. No 

 anal scent-bags. 



I have ventured to remove the Otters from the Pole- 

 cats, and unite them with the Seals, with which they so 

 nearly agree in their manner of life. The separation of 

 the Sea Otter from the fresh- water one appears to be jus- 

 tified by the characters which it exhibits. The communi- 

 cations of Sir E. HOME and Mr MENZIES (Phil. Trans. 

 1796, p. 385.), unfold several facts illustrative of its ana- 

 tomy. 



All the grinders nearly uniform in their appearance. 

 Incisors, six above, and four below. 



59. PHOCA. Seal. Without external ears. Summits of 

 the grinders flattened. Outer incisor on each side in the 

 upper jaw large. P. mtulina *. 



60. OTAIIIA (Peron). Ursine Seal. With external 

 ears. Summits of the grinders conical. External incisors 

 small. O. ursina. 



2. Without incisors or tusks in the lower jaw. 



61. TiiiCHEcus. Walrus. The tusks of the upper 

 jaw greatly produced, and directed ventrally. These aid 

 the animal in climbing upon the rocks and ice-bergs. 

 Only one species is known. T. rosmarus. 



* Some seals, as Ph, monachus, are said to have four incisors in each 

 ja\v. Such will probably be constituted into a new genus, under the title 

 Monachus. 



