relation of _Martinogale_ to _Mustela_ is presented merely to show the possibility, and not the special probability, of such an origin for _Mustela_. Knowledge of the tympanic bullae and other structures of the basicranial region would go far toward answering the question and until these structures are known [in mustelids of the Later Tertiary,] some uncertainty will remain." At the present writing I can add to the above statement only a few facts. The discovery of better material of _Bunaelurus_ than was available to previous workers led Simpson (1946), correctly I think, to synonymize _Bunaelurus_ with _Palaeogale_. Simpson figures the cranial foramina in _Palaeogale_. The differences, between _Palaeogale_ and _Mustela_, in cranial foramina, possibly are only the result of the elongation of the tympanic bullae. The bullae of the subgenus _Mustela_ are seen to be much elongated posteriorly if comparison is made with the bullae of earlier mustelids. Consequently, it might be concluded that there is nothing in the arrangement of the cranial foramina which would preclude the derivation of _Mustela_ from _Palaeogale_. However, the anterior situation of the carotid foramen--well forward along the medial margin of the tympanic bulla--is a character typical of other mustelids and the posterior location of this foramen in _Palaeogale_ might indicate that it was not ancestral to _Mustela_. SKELETON AND DENTITION The outstanding features of a weasel's skeleton are its length and slenderness. Whereas the length of the vertebral column measured from the atlas (the first cervical vertebra) to the last sacral vertebra is 175 per cent of the length of the hind leg (as measured from the head of the femur to the tip of the longest claw), the corresponding percentage is only 116 in the raccoon. Stated in another way, the vertebral column and the hind leg are of approximately equal length in a raccoon, but in a weasel the vertebral column is one and three-fourths times as long as the hind leg. VERTEBRAE The vertebral column consists of 7 cervicals, and ordinarily 14 thoracics, 6 lumbars, 3 sacrals and, depending on the species, 11 to 23 caudals. For the three species of which skeletons were examined, variations from the normal number of vertebrae are noted in the following table: TABLE I Data on vertebrae in three species of the subgenus Mustela (Numerals in parentheses indicate number of specimens)