THE MAMMALIA. 57 



EXPLANATION OF PLATE V. 



Phenacodus prim?evus (Cope) one-seventh natural size. Represen- 

 tative of type believed to be the ancestor of all hoofed mammalia, 

 monkeys, and man. Professor Cope says of the specimen, of which 

 this plate is a copy, that it is one of the most perfect fossils ever 

 discovered, almost all parts of the skeleton being preserved ; and that 

 it is one of the most important to phylogeny, as it represents the type 

 from which most modern mammalia have been probably derived. 



NOTES TO PLATES VI. AND VIl/ 



In the less specialised forms of Ungulates, the metatarsals and 

 metacarpals are not united into the so-called " cannon-bone " ; and the 

 superfluous toes are still attached to the carpals, e.g. Hipparion, 

 Anchitherium, Sus. In the highly specialised forms, the metacarpals 

 and metatarsals are united into a " cannon-bone," and the superfluous 

 toes are reduced to rudiments, known as " splint-bones," e.g., Horse, 

 Deer. 



Fig. 1 and 2. — Early form of Hoofed Animal, with reptilian brain. 

 Coryphodon hamcdns (Lower Eocene). 

 ,, 1. — Shows the right fore foot with all toes functional. 



,, 2. — Outline of Skull and Brain Cavity. 



,, 3, 4. — Early form of Horse-like Animal, Anchithrium mireliense. 

 ,, 5, 6. — Later form of Horse-like Animal, Hipparion gracilk. 

 ,, 7, 8. — True Horse. All from Les Ancestres de Animaux. 



A. Gaudry. 

 ,, 9. —Modern Pig (Sus). An unspecialised but long surviving type 



of hoofed Animal. 

 ,, 10, 11. — Unspecialised forms of Ruminants, living and extinct, 

 ,, 10, — Hyoemoschus aquaticus (living). 

 ,, 11. — Hyopotamus (extinct). 

 ,, 12, 13, 14. — Highly specialised forms of Ruminants. 



12.— Red Deer. 

 ,, 13. — Common Roe. 

 ,, 14. — Gelocus. 



.* As these plates only came to hand on the morning of going to press, 

 they cannot be inserted till our next part- 



Journal of Microscopy and Natural Science. 



New Series. Vol. II. 1889. G 



