Kalmar “genus” tana nufin matsayi na harajin da ake amfani da shi wajen rarrabuwar halittu, wanda ke tattare ɗaya ko fiye da nau’in jinsin da ke da halaye iri ɗaya da zuriyarsu. Arewacin Amurka, wanda aka fi sani da pygmy mice. Waɗannan berayen ana siffanta su da ƙaramin girmansu, gajeriyar wutsiya, da manyan kunnuwa. Sunan "Baiomys" ya fito daga kalmomin Helenanci "baios," ma'ana karami ko kadan, da "mys," ma'anar linzamin kwamfuta.Saboda haka, ma'anar ƙamus na "genus Baiomys" zai zama rukuni na haraji na haraji. kananan rodents na asalin halittar Baiomys, waɗanda aka fi sani da berayen pygmy.