Fig. 6 in Aspects of life mode among Ordovician asteroids: Implications of new specimens from Baltica

Fig. 6. Original illustration of Urasterella thraivensis; figures 83–85 from Spencer (1918) reproduced courtesy Palaeontographical Society illustrating ambulacral details. A. Ambulacrals and adambulacrals. B. Diagram of adambulacrals in lateral view. Spencer (1918) thought adambulacral orientation changed along the length of the arm. C. Spencer (1918) reconstructed inclined muscle strands between adambulacrals, see text. Abbreviations: Ad, adambulacrals; Ap, apical (dorsal in usage here) surface; D (on A), depression for muscle between ambulacral and adambulacral; D (on B and C), distal; P, proximal; Or, oral surface; Ri, transverse ridge separating successive podial basins.