FIG. 18 in Silurian and Devonian brachiopods from Severnaya Zemlya (Russian Arctic)

FIG. 18. — Selected transverse serial sections, illustrating the development of internal structures in Sibiritoechia convexa Alekseeva, 1966 (N 46/12991). Measurements: length 6.4 mm, width 6.6 mm, thickness 4.1 mm; loc. 21581, Severnaya or Pod''emnaya formations. Numerical designations are the same as on Fig. 11. Scale bar: 1.9 mm.