Figure 11 in The evolutionary diversity of barnacles, with an updated classification of fossil and living forms

Figure 11. Moulting and growth in Thoracica. Moulting occurs in the cuticular zones separating shell plates. A, new cuticle is formed by infolded epidermis in a narrow growth zone between two adjacent shell plates. B, old cuticle is shed only above the growth zone. The broken-off cuticle leaves distinct growth lines on either side of the growth zone. C, the new cuticle expands by outfolding; the growth zone is not distinct during intermoults. D, a new growth zone forms for the next moult; the shell plate can now expand laterally under the cuticle; older growth lines can thereby be included on top of the plate. Constructed from descriptions by Mahmoud (1959, 1960), Bourget & Crisp (1975) and Blomsterberg et al. (2004).