HYEACHYUS. 659 



latter may have, however, been very short and cartilaghious, and have 

 been lost. There are more or less of five sternal segments preserved; they 

 are all much compressed, the pra;sternum the most so; the prgesternum is 

 twice as long as an}- of the mesosternal segments. In general, the sternum 

 resembles that of the Bhinocerus much more than that of the horse. 



The scapula has a short but well defined coracoid process. The 

 tuberosities of the humerus are well developed, and the greater is large and 

 incurved. The bicipital groove is simple. Tlie condyles have an inter- 

 trochlear ridge and a small external condyle. The ulna and radius are 

 entirely distinct, and without proximal interlocking connection. The ulna 

 is not ver}^ slender, and its carpal articulation is not so small as in Triplopus 

 or Anchitherium. There are eight carpal bones. The pisiform is quite 

 large ; the trapezium is small. The lunar articulates with both the mag- 

 num and unciform. There are four digits in the manus, of which the second 

 (first) articulates proximally witli the trapezoides and laterally with the 

 magnum. The third (second) articulates proximally with the trapezoides 

 and laterally with the unciform. 



The pelvis is rather elongate. The ilium has a contracted peduncle, 

 and the crest is separated from the sacral plate by a long neck. The 

 ischium is without sinuses posteriorly. The femur has the great trochanter 

 produced proximad to the head, and separated from the general surface of 

 the shaft by a basal angle. The third trochanter is well developed and the 

 internal rotular crest is higher than the external. The tibia has a flattened 

 and grooved crest, bounded by a notch on the external side of the head. 

 The fibula is distinct at both extremities, and has a slender shaft. 



The calcaneiun is compressed and extends distally well beyond the 

 astragalus, thus shortening the cuboid. The trochlear part of the astraga- 

 lus is wider than in Hi/racotherium, and the head is shorter, thus resembling 

 the tapiroid and rhinocerontic rather than the equine types. The cuboid 

 facet is distinct. The mesocuneiform is a small bone, and the entocunei- 

 form is large, flat, and i)osterior in position. Tliere are three posterior 

 digits without rudiment of a fourth in the species studied, H. eximius. The 

 second and third metatarsals articulate with one carpal bone only, while the 



