Differences between populations of these Typhlops are frequently reflected in differences in the shape of head scales, particulary the rostral; these differences may be large and obvious or relatively slight. It is treacherously difficult to remember the variation of a large series and compare it with that of another, particulary when the difference involved is a matter of a slight variatipn in curvature or width. I have found certain ratios derived from measurements taken with an ocular micrometer to be of help in quantifying some of these differences.