444 Wortman — Studies of Eocene Mammalia in the 



it differs from Hymnodon, in which the coracoid is very short 

 and vestigial. The humerus, figure 87, may be said to be 

 intermediate in structure between that of the more generalized 

 Carnassidents and the opossum. In its general outline, it 

 bears a close resemblance to that of Hyomodon and differs 

 markedly from any of the Insectivora. Its chief characters 

 may be stated as follows : The head, figure 88, is not very 

 pointed behind ; the greater tuberosity is thick and rises to a 

 level with the head ; the lesser tuberosity is distinct and sepa- 

 rated from the greater tuberosity by a moderately wide bicipi- 

 tal groove ; the deltoid crest is long and powerful, extending 

 down more than half the length of the shaft ; the distal end is 

 characteristically broad, with unusual development of the 

 internal condyle and supinator ridge ; there is a large entepi- 

 condylar foramen, imperforate anconeal and anticubital fossae, 

 and a distinct division of the articular surface into trochlea 

 and capitellum. 



The bones of the fore arm are not complete, both ulna and 

 radius being represented only by their proximal and distal 

 ends. The ulna, as in Hyomodon, is much less reduced, in 

 comparison with the size of the radius, than that of the Car- 

 nassidents; it has a long, slightly incurved, and proximally 

 grooved olecranon, a deep sigmoid cavity, and a moderately 

 well-developed styloid process. The head of the radius is cup- 

 shaped, subcircular, and capable of extensive pronation and 

 supination, much more so, in fact, than that of Hycenodon, in 

 which the ulnar contact is much flattened. The distal end is 

 considerably expanded, of a trihedral form, and has a deeply 

 impressed articular surface. 



With the exception of the magnum, trapezoid, and centrale 

 of the carpus, one phalanx, and a few inconsiderable frag- 

 ments, the manus, figure 89, is complete. As compared with 

 that of a specimen of Hyamodon crucians in the Marsh col- 

 lection, the carpus agrees very closely in all the more important 

 characters. The chief osteological features of the foot may be 

 briefly stated as follows : The scaphoid, lunar, and centrale 

 are free ;* the lunar, upon its distal ulnar side, shows a consid- 

 erable articular surface for the unciform, upon which it 

 partially rests ; internal to this is a larger facet by which it 

 articulated with the head of the magnum ; the pisiform, cunei- 

 form, and unciform exhibit the usual form and relationship of 

 the more generalized carnivorous type ; the trapezium is large 



* The superior articular surface of the scaphoid is not well represented in 

 the accompanying drawing ; it should be made to extend much further for- 

 ward. 



