Hydromys

Hydromys, a genus of water-mice found in Australia, Tasmania, and New Guinea, distinguished from all other rodents by the small number ($\backslash frac\{2\}\{3\}$) of molars. They are called Beaver-rats in Tasmania; are nocturnal and very shy; inhabit the banks of both fresh and salt water, and swim well, with the help of partially-webbed hind-feet. The largest species is twice the size of a common rat. One species has the belly white, the other yellow.