Similar to the Tridacna, but distinguished from it by having its
posterior slope closed with a dentated margin; its ribs are never arched
or vaulted, and its anterior side is shorter than the posterior side.
_H. maculatus._ The spotted Hippopus. Pl. 12, fig. 1.
Shell transversely ovate, ventricose, with scaly ribs; lunule,
heart-shaped, and oblique; margins deeply crenulated; reddish purple
spots.
FAMILY XVI.
MYTILACEA. Three genera.