_Sorex merriami_ _Tamias minimus_ _Myotis thysanodes_ _Perognathus parvus_ _Myotis subulatus_ _Dipodomys ordii_ _Pipistrellus hesperus_ _Onychomys leucogaster_ _Antrozous pallidus_ _Reithrodontomys megalotis_ _Taxidea taxus_ _Lagurus curtatus_ _Marmota flaviventris_ _Lepus californicus_ _Citellus townsendii_ _Sylvilagus nuttallii_ _Citellus washingtoni_ _Sylvilagus idahoensis_ The break between the Great Basin Fauna and the other two faunas is extremely sharp, probably as a consequence of a sharp break in the flora. 2. THE PACIFIC COASTAL FAUNA. The mammals of the humid coastal district range from the Fraser River, British Columbia, southward to the vicinity of Monterey Bay, California. In Washington typical genera are _Aplodontia_, _Neurotrichus_ and _Scapanus_. The following species are typical of the Pacific Coastal Fauna in Washington: _Neurotrichus gibbsii_ _Tamiasciurus douglasii_ _Scapanus townsendii_ _Sciurus griseus_ _Sorex trowbridgii_ _Clethrionomys californicus_ _Sorex bendirii_ _Microtus townsendii_ _Marmota olympus_ _Microtus oregoni_ _Tamias townsendii_ _Aplodontia rufa_ Some species which range outside this faunal area have strongly marked races confined to it. _Glaucomys sabrinus oregonensis_ and _Lepus americanus washingtonii_ are examples. The Pacific Coastal Fauna is a forest fauna. Like the Great Basin Fauna, it reaches its northern limit of distribution in Washington and is better represented farther south. Unlike the Great Basin Fauna, the break between the Pacific Coastal and the surrounding fauna is not sharp, because forests continue into the more boreal faunal areas to the north and east. There, some mingling of coastal and Rocky Mountain faunas occurs. 3. ROCKY MOUNTAIN FAUNA. If this fauna be thought of as including mammals of the Rocky Mountains of the United States, and also those of the subarctic faunal area to the east of these mountains in Canada, the species in Washington are as follows: _Sorex palustris_ _Synaptomys borealis_ _Microsorex hoyi_ _Phenacomys intermedius_ _Lynx canadensis_ _Clethrionomys gapperi_ _Marmota caligata_ _Microtus richardsoni_ _Citellus lateralis_ _Ochotona princeps_ _Citellus columbianus_ _Lepus americanus_ _Tamias amoenus_ _Rangifer montanus_ _Tamiasciurus hudsonicus_ _Oreamnos americanus_ _Glaucomys sabrinus_