dorsal horn n.
See posterior horn.
Aboral hinge with two pyramidal caudal horns of different sizes, the dorsal horn twice as long as the ventral.
Aboral hinge with two unequal, stout, four-sided pyramidal horns; the dorsal horn half as long at the ventral.
The dorsal horn (of the smaller valve) is somewhat shorter than the ventral horn (of the larger valve).