The more important features to be presented here are: 1. There is definite proof that the retarded osseous development in congenital sporadic cretinism has its origin in utero.2. There is an apparent relationship of this osseous retardation to a disturbance of the thyroid gland in the fetus.3. Two additional cases of cretinism in one of differently sexed fraternal twins are reported, with roentgen demonstration of the occurrence of osseous retardation in utero in one case.4. The probable deductions that may be made in the physiology are discussed. North America. In his series he cited one case reported by Charles Herrman,2 in male twins, 6\m=1/2\years of age, one twin being normal. Another, though rather atypical, case was reported by Manson,3 a case of myxedema in both brothers, aged 113/2 years. Petschacher * also briefly reported the occurrence of myxedematous cretinism in 14 year old twins.As far as I know, retarded osseous development occurring in utero, however, has never been demonstrated in congenital sporadic cretinism, although both Engelbach " and Shelton°mentioned it as an aid for the early recognition of congenital cretinism.