FIG. 4. — Drawings made after SEM photos from Figures 2 and 3 in Silurian and Lower Devonian anaspids (Agnatha) from Severnaya Zemlya (Russia)

FIG. 4. — Drawings made after SEM photos from Figures 2 and 3 to illustrate different sculptures of birkeniids of the region; A-C, Birkenia? sp.; D, Birkeniida sp. C; E, G, Birkeniida sp. C1; F, I, Birkeniida sp. C?; H, Birkeniida sp. D; J, Birkeniida sp. F?; K, Birkeniida sp. G; L, Birkeniida sp. H; M, Birkeniida sp. J; N, O, Birkeniida sp. F; A, LIG 35-922; B, LIG 35-918; C, LIG 35-921; D, Pi 7570; E, LIG 35-925; F, LIG 35-929; G, LIG 35-916; H, Pi 7583; I, LIG 35-923; J, LIG 35-924; K, LIG 35-931; L, LIG 35-926; M, Pi 7573; N, LIG 35-919; O, LIG 35-914. A, C, E, I, J, L, N, sample 30-1; B, sample 30, Ushakov River; D, O, sample 157-4; F, sample 47-14, Spokojnaya River, October Revolution Island, lower part of Ust' Spokojnaya Formation, lower Ludlow; G, sample 5d; H, sample 2803; K, sample 8g-1, Pioneer Island, Ludlow; M, sample 157-3, upper part of Ust' Spokojnaya Formation, upper Ludlow, Upper Silurian. Scale bars: A-H, J-N, 0.5 mm; I, O, 0.1 mm.