Absent d triradius and dotting of the ridges in siblings.

Absent d triradii were found in 2 sibs of a family of African ancestry. 1 of the sibs exhibited not only bilateral absence of d triradius but also bilateral absence of axial triradii. The other sib lacked d triradius in the left palms. All 5 sibs of the sibship showed, to some degree, dotting or dissociation of the ridges. The present results support the suggestion of genetic transmission of both absent d triradius and dotting of the ridges.