Contained within the 3rd Edition (1957) of the Atlas of Canada is a map that shows 20 condensed maps with only mammals that are well-known to Canada. The ranges, for the most part, indicate present and usual distribution. The rare or occasional occurrences have not been shown. As there is still much to be learned about the fauna in parts of northern Canada, some range limits are hypothetical. It should not be assumed that all species may be found throughout their respective ranges as indicated on these maps, distribution within their broad ranges is frequently limited to particular but discontinuous habitats.