432 Dr. J. E. Gray on Pigs and their Skulls. 



as any of the rest, and are at once known as such by any 

 person who has an eye to the natural grouping of Mammalia. 



The division of the hoofed animals (CJngulata) into the 

 Artiodactyla and the Perissodactyla has been regarded by 

 many as an important discovery, especially by certain palas- 

 ontologists ; but if they had taken the trouble to read the 

 history of zoology they would find that these terms are only 

 Greek names for groups recognized and named in Latin by 

 Ray, Lati-eille, and others. 



It is amusing but sad to see the various explanations and 

 the different theories which are put forth to make the tapirs, 

 that have four toes before and three behind, and the horse, that 

 has only one toe, odd-toed Ungulates or Perissodactyla, like 

 the rhinoceros, that has only three toes on each foot ; and they 

 have been obliged to put Hyrax and the elephant into a 

 separate order, because it is rather difficult to explain into 

 which it ought to go (see Flower's 'Osteol. Mam.' pp. 264-267, 

 figs. 90-98). 



At the same time I do not at all underrate the importance 

 of observing the structure and proportion of parts in the ar- 

 rangement and definition of the minor groups. Thus it would 

 appear that the equality of the two middle toes, which repre- 

 sent the middle and ring fingers of the human hand, is an im- 

 portant character in the Pecora or ruminant animals, and in 

 the pigs (Setifera) and the Obesa (Hippopotami); while the 

 greater length and thickness of the middle toe, representing 

 the middle finger of the human hand, makes a modification in 

 the form of the feet of these animals — especially as this toe is 

 always present, while one or more of the side toes may be 

 rudimentary or entirely absent, as may be expressed in the 

 following table : — 



Toes of fore feet. Toes of hind feet. 



Elephas 1, 2, 3, 4, 5. 1, 2, 3, 4, 5. 



Hyrax 0, 2, 3, 4, 5. 0, 2, 3, 4, 0. 



Tapirus 0, 2, 3, 4, 5. 0, 2, 3, 4, 0. 



Rhinoceros 0, 2, 3, 4, 0. 0, 2, 3, 4, 0. 



Equus 0, 0, 3, 0, 0. 0, 0, 3, 0, 0. 



Sometimes, as in the elephant, the middle toe is very little 

 longer than the rest. 



The name Perissodactyla has been given to the three latter 

 genera ; but I cannot conceive a slight difference in the propor- 

 tion of these toes to be of ordinal importance. It is no doubt 

 an important character in the definition of minor groups, but 

 scarcely of higher importance, as having little influence on the 

 habits and manners of the animals, and as separating groups 



