362 SCOTT. [Vol. XI. 



height of the distal tarsals. If Kowalevsky's figure of the pes 

 be correct, Geloctis probably is behind Protoceras in the reten- 

 tion of the distal portion of the lateral metatarsals. However, 

 neither this writer nor Filhol speaks of finding these portions 

 in situ, and, if their association with the pes is conjectural, no 

 great stress can be laid upon this character. 



The result of this comparison, then, is that in regard to the 

 structure of the skull, and to a less degree the dentition, Pro- 

 toceras is far in advance of Gelociis, while the differentiation of 

 the limbs, and especially of the feet, lags as far behind. This 

 association of characters confronts us with very clearly defined 

 alternatives, when we attempt to solve the problem of the rela- 

 tionship of Protoceras to the Pecora. Assuming, as we have 

 every justification in doing, that Gelociis is an ancestral form of 

 the Pecora, then, either Protoceras is not descended from 

 Gelociis at all, and its likenesses to the Pecora are not due to 

 genetic affinity, but have been independently acquired ; or, on 

 the other hand, Protoceras is so descended, its resemblances to 

 the true ruminants are the expression of real relationship and 

 the primitive structure of the limbs and feet has been reac- 

 quired, whether by reversion or otherwise. Of these alterna- 

 tives the former is by far the more probable, (i) Without at 

 all denying the possibility of such reacquisition of primitive 

 characters, yet no plausible reason can be assigned for assum- 

 ing it, and no case is known, among mammals at least, in 

 which such a mode of development has been rendered in the 

 smallest degree likely. (2) On the other hand, very many 

 cases of the independent acquisition of similar structures have 

 been pretty clearly demonstrated. It will suffice to mention 

 the many different groups which have independently developed 

 the spout-shaped odontoid process of the axis, or the tetrase- 

 lenodont molar, or the humerus of the horse and camel. It 

 may, perhaps, be objected that these are single characters, 

 whereas the skull of Protoceras displays a whole series of such 

 resemblances to the Pecora, but even such cases of parallelism 

 are by no means unknown. There are many close correspon- 

 dences in the skull-structure (and limb-structure as well) 

 between the camels and the true ruminants, and yet the sue- 



