Novak considered this form within the range of variation of Cellepora depressa, Hag., but Canu recognizes it as a Rhagasostoma. It appears to be so closely related to a very distinct and persistent form which is very abundant and characteristic at Trimingham that I do not like to treat them as anything but two forms of a single hitherto unnamed species, and the form admirably figured by Novak must of course be the type of the species.