4 CONTENTS OP A BONE CAVE. 



The distal end of the humerus is not expanded, having small epicondyles. The 

 trochlear face is strongly concave, ending in a deep olecnmon, but no coronoid 

 fossa. The bridge over the elongate arterial foramen is narrow. 



The head of the femur is well bounded by a neck. The great trochanter rises 

 as higli as the head, and is deeply concave behind. The little trochanter is a 

 prominent tuberosity on the posterior face of the bone. The shaft is slender and 

 subcylindric. The condyles are somewhat compressed, and their surface is continu- 

 ous with that of the patellar groove. The latter is longer than wide, moderately 

 concave, with equal borders, which rise higher than the level of the shaft. 



MEASUREMENTS. 



If. 



Diameter of head of humerus ...... .007 



" of shaft of humerus ...... .008 



of epicondyles of humerus ..... .016 



" of head of femur ...... .009 



" at little trochanter of femur . . . . .012 



" of shaft of femur . .... .008 



" of condyles of femur . . . . . . .017 



AMBLYRHIZA, Cope. 



Proceedings of the Philadelphia Academy, 1868, p. 313. Proceed. Amer. Philosoph. Society, 1869, 

 p. 183. Loxomylus, Cope, Proceed. Amer. Philos. Sou., 1869, p. 186. 



The characters -of this genus are derived from the study of the remains of ten 

 or more individuals of three species. These include portions of all parts of the 

 skeleton with some important exceptions. There are wanting the superior, and parts 

 of the inferior walls of the skull ; the anterior foot, the distal parts of the pelvis, 

 the calcaneum, and the ungual phalanges. 



Skull and Teeth. A fragment preserved includes the occipital condylo, with 

 the mastoid and petrous bones. The condyloid foramen is pierced through the 

 rather thin basi-occipital. The mastoid region is produced downwards and back- 

 wards, but the specimen being broken does not indicate its length. The petrous 

 bone is in contact with the basi-occipital, closing the foramen lacerum posterius. 

 Its inferior wall is not expanded bulla-like, but is flat and thick. The mcatus 

 auditorius externus is continued by the thick tympanic bone, in tubular form 

 backwards and outwards. The apex of the petrous bone is truncate, and is deeply 

 notched for the foramen. The premaxillary bones and the symphysis mandibuli 

 are much produced and narrowed, and were probably inclosed in fur-bearing in- 

 tegument, as in the existing chinchillas. The mandibular rami are completely 

 coossified. They are united at their lower borders, posterior to the divergence of 

 their dental ridges, by the expansion of the stout rib of the inner face of each, 

 which incloses the incisive alveolus. This ridge extends posteriorly very far ; in 

 the A. latidens to a point behind the last molar and even posterior to the base of the 

 coronoid process. The latter is very short, and forms a flat process extending 

 obliquely outwards from the ramus. The condyle of the mandible is narrow, and 



