Orthonychia enorme (Lindström, 1884) in thin sections, Silurian Eke Formation, Gotland; the type of preservation of the shells suggests that they were primarily calcitic with foliated micro-structures; some of the shells have very long frills; these frills are much longer than those on specimens from the type series (Figs 3–5) and washed samples (Figs 7–8) suggesting they broke off during weathering and the processing of the samples. Thin sections reposited Friedrich-Alexander-Universität Erlangen-Nürnberg, GeoZentrum Nordbayern, Erlangen, Germany. (A) Shell in longitudinal section, specimen with pronounced frills. (B, C) Shell in longitudinal section, specimen with pronounced frills in apical portion (C). (D) Shell in longitudinal section, specimen shows coiling in its apical portion. (E) Upper portion of image, shell in transverse section of one whorl (large oval) and tangential to earlier whorl (round). (F) Middle left portion of image, shell in transverse section of one whorl (left large oval) and earlier whorl (right circular). (G) Shell in longitudinal section, specimen shows pronounced frills covered by a thick microbial crust. (H) Shell in transverse section, covered by a thick microbial crust. (I) Shell in longitudinal section, covered by a thick microbial crust.