Hassalstrongylus dollfusi. A, male, anterior extremity, left lateral view. B, female, head, apical view. C–H, synlophe in transverse sections of the body: C, D, at oesophago-intestinal junction, C, male, D, female; E, F, at mid-body, E, male, F, female, (1) this work, (2) modified after Durette-Desset (1969); G, male, at level of spicules; H, female at level of uterus. Abbreviations: L, left, V, ventral. Arrow represents the axis of orientation of the ridges. All sections oriented as in E.