264 0. P. Hay — Fossil Turtles in the Marsh Collection. 



vated. Seen from the side, the maxilla is convex on its lower 

 border. The premaxillae are distinct from each other and from 

 the maxillae. At the symphysis they are only 3 mm high, but 

 at their union with the maxillae, 10 mm high. As in the Bridger 

 species, there are distinct lachrymal bones. They occupy the 

 position of the descending portion of the prefrontals of other 

 turtles, coming in contact with the vomer. 



As seen from below, the maxilla has a broad masticatory sur- 

 face, its width from the inner border to the cutting edge being 

 14 mm . The inner border of this surface is furnished by the 

 palatine bone. The latter forms the whole of the outer border 

 of the choana. The masticatory surface does not extend for- 

 ward on the premaxilla. In front of the choanae there is a deep 

 groove, which anteriorly expands on the lower surface of the 

 premaxillae. Postpalatine foramina are present. 



The pterygoids come in short contact with the maxillae. 

 They have distinct ectopterygoid processes. Where the pos- 

 terior part of the palate is constricted, it is 18 mm wide. The 

 pterygoids extend backward to the posterior border of the 

 pedicel of the quadrates, thus separating the latter widely from 

 the basioccipital and basisphenoid. There is a considerable 

 groove on each side between the quadrate and the median bones 

 of the base of the skull. The pterygoids join at the midline 

 for some distance in front of the basisphenoid. On each side 

 of the latter, about the middle of its length, is a foramen. 



The pedicels of the quadrates are short. The surface for 

 articulation with the lower jaw is deeply concave from side to 

 side ; nearly plane from front to back. 



The quadrate bone is notched behind for the passage of the 

 stapedial rod. 



There appears to have been a system of epidermal scutes 

 covering the upper surface of the skull. Not all the areas 

 occupied by these can be made out with certainty, but some of 

 them are quite distinct. A pair of these seems to have occupied 

 the space between the orbits. Behind each of these is a smaller 

 one which lies over the hinder border of the orbit. A very 

 large scute, or more probably a pair of them, covers the area 

 of the frontal bones and overlaps on the parietals. The pos- 

 terior half of this scute or scutes is separated by two scutes 

 occupying the midline. One of these, the anterior, is small 

 and circular ; the other is elongated and extends backward on 

 the supraoccipital processes of the parietals. It is, of course, 

 possible that the latter scute was divided along the midline. 



The study of this skull confirms the view of Dr. George 

 Baur, drawn from the skull of Co?npsemys plicatula, that there 

 are in the skulls of the Amphichelydia few pleurodiran charac- 

 ters. Nasals are indeed present, but they • can hardly be 



