Key for identification of species of genus Boreochiton

1(2) Tegmentum granulated ..................................................................... B. granulatus.

2(1) Tegmentum smooth with growth lines only.

3(4) Head of major lateral tooth of radula higher than its own width. Ratio of width of apophyses to width of jugal sinus 1.1–1.3 ........................................ B. jakovlevae.

4(3) Height of head of major lateral tooth of radula less than its width. Ratio of width of apophyses to width of jugal sinus 1.4–2.6.

5(8) Dorsal spicules large, more than 60 µm in middle part of girdle, densely cover girdle. Numerous bristles up to 140–320 μm. Girdle orange-red, its surface rough and granulated.

6(7) Length of antemucronal area equal to or oftenly more than length of postmucronal area. Girdle 1.7–2.0 times narrower than width of valve V. Bristles up to 320 μm height. Dorsal spicules 55–60 μm. Height of head of major lateral tooth less than its width ............................................................................ B. beringensis beringensis.

7(6) Length of antemucronal area less than length of postmucronal area. Girdle 2.8–3.8 times narrower than valve V. Bristles up to 140 μm height. Dorsal spicules up to 80 μm. Height of head of major lateral tooth equal to its width .............. B. ruber.

8(5) Dorsal spicules small, about 40 µm in middle part of girdle. A few bristles up to 50 μm cover girdle. Girdle light with leathery surface ...... B. beringensis lucidus.