Aglaophenia postdentata Billard, 1913

The most characteristic feature of Aglaophenia postdentata and the one used by Billard (1913) to distinguish it from A. pluma (Linnaeus, 1758), is the very long median adcauline tooth of the hydrothecal margin. In the present material, this tooth is much longer than that figured by Billard (1913). The manner in which this, and the other apertural teeth arch over the hydrotheca, and the outrolled, leaf-shaped paired laterals, is diagnostic of the species. However, without careful examination from all angles these features are often very difficult to see.