MAMMALS. 



397 



The ANTHRACOTHERIID^:, best developed in the European upper eocene, 



have the teeth / 



\, /// f , the metapodials distinct, and four toes on 



each foot, the outer ones in process of reduction. Anthracotherinin, eocene. 



Hyopotamus, miocene of the U. S. and Europe. The SUID^J, or swine, 



apparently derivatives of the last family, appear in the eocene of both conti- 



nents, and continue to the present time. They have the teeth i f or f , c \, 



P \ to f , m f , the molars bunodont. The feet are four-toed, rarely three- 



toed, toes 2 and 5 smaller than the others, and the metapodials distinct. 



The stomach has a pouch developed near the cardiac opening ; the colon is 



spirally coiled, and a caecum is present. The earlier history of the family is 



less certain than that of some others, and some of the earlier genera seem to 



have a carnivorous facies. The family to-day belongs to the old world, only 



the peccaries (frequently set aside as a distinct family, DICOTYLTD^E) occurring 



in the western hemisphere. In 



Achanodon, from the eocene, there 



are already developed the tusk-like 



canines so characteristic of mod- 



ern swine ; in Elotherium they are 



less conspicuous, while in Chocro- 



potamus (eocene, Europe) and 



Leptochcerns (miocene, U. S.) 



these teeth are smaller. The pec- 



caries (Dicotyles} appear in the 



American pleistocene, and two or 



three species persist in warmer 



America to-day. They have the 



teeth i f , c j, p \ , m f ; the fifth 



toe of the hind feet lacking, and 



the stomach more complex than 



in the typical swines. The spe- 



cies are gregarious and omnivor- 



ous. The allied Platygonus is 



pliocene. In the pigs proper 



Sns, Babirusa. Phacochoeriis the 



canines are greatly developed and triangular in section, and a large diastema 



exists between these and the premolars. All are old-world forms, and are dis- 



tinguished by the dentition : Sus, /-|, c \, p |-, m ^ ; Babirusa, i \,c\,p\* M f ; 



Phacockcerus* i\, c\,P f, m \- The true swine, Sus, appear in the pliocene 



and continue as our domestic hogs, descended from the wild boar and other 



Asiatic species. The single species of Babirusa (Porcits} of the Malay Islands 



is remarkable in that the upper canines of the male grow upward through the 



skin of the snout. The wart-hogs of Africa (Phacockcerus] receive their 



common name from the projections on the face. In the adults many of the 



teeth are lost, but the canines form enormous tusks, both pairs curving 



upwards and outwards. 



The HIPPOPOTAMID^E are large, amphibious, bunodont forms, with teeth 

 / I to f, c \, p |, m f , th^lower incisors very long and rootless. The metapo- 

 dials are distinct, the feet four-toed, the lateral toes being nearly equal to the 



FIG. 367. Stomach of sheep, after Carus^ 

 and Otto (Oppel). a, abomasum ; o, oma- 

 sum; re, reticulum; ru, rumen. 



