THE AMERICAN NATURALIST. [Vol. XXXVII. 



aquatic life. The following list, though making no pretensions 

 to completeness, will serve to indicate how great and varied a 

 number of forms have become, either from choice or necessity, 

 more or less aquatic. 



Cetacea, the entire order. 

 Sirenia, the entire order. 

 Carnivora, 



Pinnipedia, the entire suborder. 

 Fissipedia, 



Lutra, the various species of otters. 

 Enhydris (Latax), the sea-otter. 

 Putorius, the mink and sumpfotter. 

 Rodentia, many scattered examples, as — 

 Myocastor (Myopotamus). 

 Hydrochcerus, the capybara. 

 Hydromys, the Australian water-rat. 

 Hydrochilus. 



Microtus (Arvicola) the water-vole. 

 Ichthyomys. 

 Castor, the beavers. 

 Fiber and Neofiber, the muskrats. 

 Insectivora, many scattered examples, as — 

 Myogale, the desman. 

 Crossopus (Sorex) the water-shrew. 

 Neosorex, the American water-shrew 

 Chimarrogale. 

 Nectogale. 

 Potamogale. 

 Limnogale. 



Ungulata, 



Artiodactyla, 



Hippopotamus. 

 Marsupial a, 



Chironectes, the water-opossum. 

 Monotremata, 



Besides these there might be mentioned among extinct forms 

 the Zeuglodontidae, thoroughly aquatic animals doubtfully related 



