Hay (1908) described among the soft shell turtles of the genus Aspideretes from the Bridger Eocene a form, A. grangeri Hay, the carapace of which exhibits an unusually shaped first and second pair of costal plates. The first pair is proximally wide, distally narrow, the second pair shows opposite proportions. Hay (loc. cit.) describes this feature, pays little attention to it, however, assuming that it is a mere variation. In 1940 the writter collected an almost complete shell, carapace and plastron, of a form which resembles A. grangeri Hay in the similarity of proportions of the first two pairs of costal plates. The differences between the two shells are, however, numerous and the proposal of a new species seems well justified. The species is dedicated to my wife, Ann, who discovered the fossil. The specimen was embedded in a gray clay, dorsal side up. The shell was disarticulated to some extent and strewn over an area of about two square yards. Some limb bones and fragments of vertebrae were associated with the shell plates, but there was no indication of the presence of the skull. Some of the plates lay piled up on one another, others w'ere found some distance away from the main mass of bones. The state of preservation of the fossil in the formation recalls similar deposition of skeletons in the marine Triassic (Scisti bituminosi) of Mt. San Giorgio, Tessin, Switzerland, where entire skeletons often are totally disarticulated; Peyer 1935 (Paraplacodus broilii Peyer; type and specimen B); 1936: Hescheleria ruibeli Peyer, type. There can be no doubt that the general conditions of burial-in the case of the marine Triassic fossils on one hand and the present turtle from the Bridger Eocene of Wyoming on the otherwere very different. A comparison of the similarities and dissimilarities of preservation and deposition in the two cases, however, may aid in the reconstruction of the probable burial circumstances of the present fossil. In both cases the skeletons are completely disarticulated, yet the bones are not irregularly mixed together, but retain in general their original position in regard to the regions of the skeletons to which they belong. Furthermore the dislocation of bones took place in one direction only, in Hescheleria riibeli Peyer from side to side, in A. annae parallel to the longitudinal axis of the body. The fact that almost entire skeletons, totally disarticulated, remained preserved in a restricted area, strongly sugQests that they w' re partially or completely embedded in mud before the final decomposition of the ligaments took place. In the case of the Triassic skeletons from Mt. San Giorgio it is frequently observed that the side of the skeleton which faces down in the formation (and which was facing the sediment at the time of burial) is better,