The boss covers the junction of four ribs and is carved with an elongated human head. The eyes are half-closed, the tongue appears to protrude, and the hair falls in stiff curls around the ears. The end of each of the ribs is keyed to allow closer bonding to the adjoining sections of rib, and the back of the stone is worked flat. The profile of each rib consists of a broad frontal fillet flanked on each side by a chamfer, an offset, another chamfer and the vertical side of the rib.