Ectenagena magnifica
Shell white, brittle, elongate-ovate, with the right and left valves equal in size, outline and inflation (equivalve). Umbones at the anterior third, with the beaks poorly defined. Periostracum brown, dehiscent (absent from the older portions of the shell). External sculpture of irregular commarginal growth increments generally restricted to the margins of the shell flank. Internal surface and margins smooth. Pallial sinus absent. Ventral surface of the hinge plate with a series of small scars. Ligament external, supported by nymphal ridges, extending along most of the postero-dorsal margin of the shell. Hinge teeth represented by irregular cardinals; lateral teeth absent.
Boss and Turner (1980) described the anatomy of the species. Below is a summary of their observations:
Mantle: Pedal aperture large. Middle mantle fold with short papillae. Short, separate incurrent and excurrent siphons formed by fusion of the inner mantle folds.
Foot: Large, with byssal groove and gland, but no byssal threads produced by adult specimens.
Gills: Large, flat (non-plicate), with inner and outer demibranchs displaying both lamellae. Formed by filaments of identical morphology (homorhabdic).
Digestive tract: Labial palps very small. Rectum passes through the pericardial cavity and the ventricle of the heart.