Study of Os japonicum in Uttar Pradesh crania.

The incidence of Os japonicum has been studied in 500 Uttar Pradesh crania, and is found to be 4%. Typical bipartile zygomatic bone das present in 40 instances. In 6 bones only a horizontal groove was seen on the temporal surface. In one skull the zygomatic process of maxilla and the zygomatic process of the temporal bone were articulating directly on the temporal surface of the zygomatic bone. In another skull the maxilla and the temporal bone were articulating with each other along the lower border of the zygomatic bone, giving the appearance of a tripartile condition. The cause and significance of this trait is discussed in the light of available literature.