Absence of triradius d on the palms of normal people.

Absence of the digital triradius d is a very rare phenomenon, previously only reported in abnormal XXXXY males. During the past few years the anomaly has been found on the palms of three normal females, namely a young English woman and two sisters in the Nicobar Islands in the Indian Ocean. These cases are described and illustrations of the palmar dermatoglyphics presented. The occurrence of such a rare phenomenon in two sisters suggests that it is genetically determined.