Circeis paguri Phyllis Knight-Jones (Knight-Jones & Knight-Jones, 1977) differs from
C. armoricalla and all spirorbids so far studied in that all the larval eyes are small rounded
ocelli. The species breeds from February to August. Some of those attached to the telson
bear embryos and may thus be transferred to new shells by the hermit-crabs without any
need for a pelagic stage. The attached tubes are concentrated it) the roof of the penultimate
whorl. Mean size, numbers and breeding potential are greater within larger shells.