In Calceola sandalina the full complement of counter major septa was established very low in the calyx, extending from the counter septum across to the edge of the counter face. At about mid-height of the calyx, a counter-lateral major septum was generated on either side of and from the counter septum. Serial minor septal insertion was initiated adjacent to the counter-lateral septa at a slightly later stage and continued throughout the subsequent ontogeny of the corallite, with minor septa (schizosepta?) arising on the median side of major septa and bifurcating from them. Alar fossulae are seen in the calyx of mature corallites, on the counter side of a low ridge near the lateral extremity of the inner surface of the counter face. Insertion of major septa in the alar fossula has been observed rarely on the external counter face of worn corallites. The median septum in the operculum of C. sandalina is a compound structure which incorporates adjacent minor septa. In an Emsian(?) corallite of ?Chakeola sp. minor septa are derived from major septa, new minor septa being generated on the outer side of major septa. This corallite also exhibits minor septa adjacent to the K septum, thus casting doubt on Birenheide’s generalisation that the counter-lateral septa of C. sandalina are not separated from the counter septum by minor septa. In the Emsian Chakeola whitehousei minor septa are present adjacent to the counter septum of the operculum. The distal, anteriorly facing, projecting peg of the K septum of the corallite articulated within the large socket in the opercular K septum, and subsidiary grooves and plates on the socket and septum further facilitated interlocking. Knobs and/or small lists are developed along the posterior edge of the operculum, in the shelf inside the counter edge; septal pegs developed by septa in the corallite were accommodated within this shelf. The opercular septal blades interlocked loosely between the anteriorly facing, distal parts of septa of the corallite. Rare opercula show one or more (abortive?) attempts to overcome damage which led to displacement of the operculum relative to the corallite, and rejuvenescence is exhibited to various degrees in many opercula. One operculum was apparently broken (bitten?) in half as a juvenile, but was reconstructed to reach a mature form. Other specimens show epifauna, borings and bioerosion either on the external surface of the operculum or on the external cardinal surface of the corallite. ‘Galls’ on the inner opercular surface are interpreted as stereome deposited to seal off some type of internal parasite. In C. sandalina, tubules containing tabulae are located just inside the counter face, and may have served to house soft parts associated with the operculum. Changes of opercular septal morphology suggest that the phylogeny of Devonian genera of the Calceolidae is Rhizophyllum → Savageola → Chakeola → Richtereola and ultimately, → Calceola.