This data was analyzed the process of Kerckring on the occipital bone of numbers black and white perinates. The process of Kerckring is a projection of bone occasionally observed emerging from the inferior margin of the supraoccipital portion of the occipital squamous at the midline. Its status was regarded as either absent or present.
data(kerckring.df)S. M. Weinberg, D. A. Putz, M. P. Mooney, and M. I. Siegel. Evaluation of non-metric variation in the crania of black and white perinates. Forensic Science International, 151(2-3):177-185, July 2005.