Mites of the genus Schizocarpus Trouessart, ,1896 (Acari. Chirodiscidae) parasitic on Castor canadensis from Alaska, USA were studied as compared with those from Indiana. Nine new species are described, three in the mingaudi group: Schizocarpus paramingalldi n. sp., S. alaskensis n. sp., and s. reductus n. sp.; four in the indianensis group; S. postannulatus n. sp., S. centralis n. sp., S. contrarius n. sp .. and S. distinctus n. sp.; and two in the virgulatus group: S. protinus n. sp. and S. posticus n.-· sp. These data support previous conclusions on European and Indiana Beavers concerning multispeciation in the genus Schizocarpus related to isolation of the Beaver populations in separate areas and relative confinement of the mites to definite areas of the Beaver. Observed differences in this genus are in the males; it is suggested that mUltispeciation evolved as a means of species recognition.