ABSTRACT
Lamarck and some other authors have placed the species of Chelonobia under Coronula, but this has arisen, as explained under that genus, from a misapprehension of their structure. The folded very thin walls in Coronula compared with the radiating septa of the very thick walls in Chelonobia. In Coronula the opercular membrane is stretched like the skin of a drum, almost horizontally across the top of the shell. It is attached to the sheath rather lower down at the carinal than at the rostral end: hence the animal's body, as remarked by Burmeister, is attached almost horizontally; under Xenobalanus and Tubicinella, cannot be considered a character of much importance. Coronula Barbara, a form closely allied to C. diadema, existed during the Red Crag period; and Bronn has described some fossil specimens from Italy. Coronula reginae is much more related to C. diadema than to C. balaenaris, and suspect that it replaces in the Pacific the former of these two species.
