B. extra (Christiansen & Bellinger, 1980)

– Proisotoma (Ballistura) extra Christiansen & Bellinger, 1980: 586

AK Weber 1950; Hurd & Lindquist 1958 both as Guthriella sp.; MacLean et al. 1977 as Proisotoma schötti; Christiansen &

Bellinger 1980, 1998; Danks 1981 as Guthriella sp.; Skidmore 1995; Babenko & Fjellberg 2006

Remarks: This species is very similar to the Eastern Palaearctic B. wrangeliensis Martynova, 1973, originally described from the other side of Bering Strait (from Wrangel Island). The separate status of these species needs confirmation.

General distribution: Nearctic.