No. 2.] THE RELATIONS OF PROTOCERAS. 36 1 



of that group has any such protuberances, their horns and 

 antlers always rising from the frontals. 



The other parts of the skeleton bear testimony of similar 

 import. The atlas and axis do not differ in any important 

 respect from those of Geiocus, so far as the latter are known. 

 In particular, the odontoid process has attained the same stage 

 in the development of the spout-like shape. The remaining 

 cervical and the thoracic vertebrae are very similar to those of 

 the musk-deer, while the lumbars are more traguline. 



The limbs are in almost every res'pect far more primitive 

 than those of Geiocus. The scapula, however, has a more 

 modernized form than in that genus, and except for its more 

 prominent and recurved spine, is a copy of that of the musk- 

 deer ; while in Geiocus it is wider than in either the recent 

 tragulines or true ruminants. The fore-arm bones are decidedly 

 less advanced than in Geiocus. In the latter the groove on the 

 proximal end of the radius for the intercondylar ridge of the 

 humerus is much narrower, the distal facets for the carpus are 

 much more oblique in position, and there is an articulation 

 with the cuneiform. The shaft of the ulna is much more 

 reduced, and its distal end no longer covers the entire cunei- 

 form. The carpus of Geiocus shows a great advance over 

 that of Pj'otoceras, both in its reduced vertical height and 

 in the ankylosis of the trapezoid and magnum. In the meta- 

 carpus the same advance is visible in the reduction of the 

 lateral digits to splint-bones, which are interrupted in the 

 middle, in the exclusion of the second metacarpal from contact 

 with the magnum, and the articulation of the third with the 

 trapezoid. In all these respects Protoceras is very much more 

 primitive. Filhol adds another modernization of Gelociis, viz., 

 the frequent coossification of the proximal parts of the lateral 

 metacarpals with the median pair, although the latter are not 

 themselves ankylosed to form a cannon-bone. 



Femur, tibia, and fibula show no important differences in 

 the two genera, but the pes of Geiocus is much more modern- 

 ized. This advance consists in the coossification of the cuboid 

 and navicular and the coalescence of the third and fourth 

 metatarsals into a cannon-bone, as well as in the reduced 



