Describes the Sorex cinereus, or masked shrew. Order Insectivora; Family Soricidae; Subfamily Soricinae; Similarity to Sorex fontinalis, Sorex haydeni, and Sorex longirostris; Small, brown long-tailed shrew; Males and females are larger in northeastern part of range, along the cost in Pacific Northwest in the United States and in central Canada; Distribution; Form and function; Fossil record.