Retroplumidae Gill, 1894

Retropluma quadrata de Saint Laurent, 1989 (Fig. 23)

Ossicles I and II are inclined about 45° in the antero ventral direction. The zygocardiac ossicle (V) has a clear semicircular impression antero ventral. The unpaired propyloric ossicle (VI) is nearly vertical. The pectinal ossicle (VIII) is horseshoe-shaped with six accessory teeth. The ossicle XIXa is not recognisable.