This case is reported not only because of its apparently extreme rarity, but also because it may serve as a stimulus to further investigation of the factors responsible for defective development of the ectoderm. A convenient opportunity is also afforded to discuss certain phases of the function of the skin on which modern physiologists and dermatologists still disagree. Our case is the second of its kind reported in the American literature and the sixth reported in the world's literature. It stands absolutely unique, however, in the fact that the developmental defect occurred in a female; all other cases reported occurred in the male. The significance of the latter fact will be apparent from subsequent discussion. It would seem, however, that the extreme rarity of this type of case is more apparent than real. All evidence in the literature points to the fact that the extremely high grades of ectodermal defect