Pterostoma

1 Transition region represented by 5–7 bands of cells with flat cell floors (Fig. 89)............................. P. sinica

- Transition region represented by 7–9 bands of cells, where first 3–4 bands are prominent and with deeply concave, folded cell floors, following 4–5 bands with flat cell floors (Figs. 33, 90)...................................................2

2 Russia (Transbaical, Amur, Primorye), Korea, Japan, China ............................................. P. griseum

- From Europe to Chita Region (Russia), Turkey, Transcaucasus, Azerbaidshan, Iraq, Iran ...................... P. palpina