scill

scill, f.n: a shell, shellfish; the shell of an egg, a scale of a fish, serpent, etc. (SHILL / ˈʃɪl)

A fairly unconvincing but amusing drawing of a mollusk poking its head out of its spiky shell.
A collection of medical texts including Tractatus de herbis; Italy, c. 1280-1350; British Library, Egerton MS 747, f. 18v. [iiif.bl.uk]