50 GENERAL EYOLUTIOK 



op a basal snag of the antler (see Cuvier, " Ossem. Fossiles"; 

 Gray, " Catal. Brit. Mus.") at the third year ; a majority of those 

 of the 'New World (genera Cariaciis, Subulo) never develop it 

 except in ^'abnormal" cases in the most vigorous maturity of the 

 most northern Cariacus (C. virginianus) ; while the South Ameri- 

 can Subulo retains to adult age the simple horn of the second 

 year of Cervus. 



Among the higher Cervidae, Rusa and Axis never assume char- 

 acters beyond an equivalent of the fourth year of Cervus. In 

 Dama the characters are on the other hand assumed more rapidly 

 than in Cervus, its third year corresponding to the fourth of the 

 latter, and the development in after years of a broad plate of 

 bone, with points, being substituted for the addition of the corre- 

 sponding snags, thus commencing another series. 



Returning to the American deer, we have Blastocerus, whose 

 antlers are identical with those of the fourth j^ear of Cariacus. 



Now, individuals of the genus Cervus of the second year do 

 not belong to Subulo, because they have not as yet their mature 

 dentition. Rusa, however, is identical with those Cervi whose 

 dentition is complete before they gain the antlers of the fifth 

 year. When the first trace of a snag appears on one beam of 

 Cariacus virginianus, the dentition includes the full number, but 



there remain - milk molars much worn and ready to be shed. 



Perhaps the snag is developed before these are displaced. If so, 

 the Cariacus is never a Subulo, but there can be little doubt that 

 the young Blastocerus belongs to that genus before its adult char- 

 acters appear. 



7. Leidy states * that certain Perissodactyl remains, contain- 

 ing a foot of a horse, contained the teeth of a genus, Protohippus, 

 which has the permanent teeth of Equus, and the deciduous 

 dentition of Anchitherium. He observes : *^The deciduous and 

 permanent dentitions of both these genera are alike ; therefore 

 the new genus is in early life an Anchitherium, and later in life a 

 true horse." This is therefore a case of exact parallelism, always 

 providing that the Protohippus has not added to its immature 

 equine characters others in other parts of the body, which in- 

 validate the identity. In the latter case it will still be an inter- 

 esting example of the *^ inexact parallelism." \ 



* "Proceed. Acad. Xat. Sci," 1858, p. 7. 



f This is not a proper example of parallelism if, as some zoologists believe, the 



