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HIPPOTHERIUM 



51 



Length of radius 245 mm. 



Proximal articular breadth . ■. . . . • 57 " 



Distal articular breadth, including ulna . . . . 46 " 



The metacarpal, shown in plate xix. fig. 9, is long, slender, and round, 

 with roughened surfaces for the contact of digits II. and IV. continued down 

 the posterior face for the greater part of its length, with a well-defined ridge 

 between them. The trochlear keel runs completely around the distal articular 

 surface, which terminates anteriorly in a considerable hollow. 



Length of metacarpal ....... 230 mm. 



Width of proximal articular face . . . . • 35 " 



Width of distal articular face . . . . . . 31 " 



The distal end of a tibia, plate xix. fig. 5, presents no peculiarities, and 

 measures as follows : 



Greatest width . . . . . . . . -56 mm. 



Greatest antero-posterior diameter on intei'nal face . ■ 37 " 



Greatest antero-posterior diameter on external face . . 28 " 



The astragalus, plate xviii. fig. 14, has the proximal and distal internal 

 tuberosities well developed, even more so than in the horse, differing in this 

 respect from the astragalus of H. isosensum described by Professor Cope. 

 On a larger scale it resembles the astragalus of H. gratitm, previously de- 

 scribed. 



Its measurements are : 



Height of internal face ....... 49 mm. 



Breadth of cubo-navicular face . . . . . ■ 37 " 



Two fragments of metatarsals belonging, if not to the same individual, to 

 two of the same size, indicate the length of this bone to have been about 

 235 mm. The proximal end, plate xix. fig. 7, is cut out for the second and 

 fourth digits, and the articular faces for these metatarsals extend the entire 

 length of the bone. They are more widely separated, except at their proximal 

 ends, than the second and fourth metacarpals, and instead of a ridge are 

 divided by a shallow groove. The trochlear ridge runs completely around 

 the distal articular face, being carried well up behind, where it is also the 

 most prominent. This articulation terminates anteriorly in a very shallow 

 depression, instead of in a very deep one, as is the case with the distal articular 

 face of the metacarpal. The width of the distal articular face is 30 mm. 



