THE PAL^OTHEEID^. 365 



and the coat of cement very tliin. The molar tooth of the 

 Tapir thus represents the plan of structure common to 

 the Perissodactyla in its simplest form. Deepen the valleys, 

 increase the curvature of the wall and laminae, give the 

 latter a more directly backward slope ; cause them to de- 

 velop accessory ridges and pillars, and increase the quantity 

 of cement; and the upper molar of the Tapir will gradually 

 pass through the structure of that of the Rhinoceros to 

 that of the Horse. 



In the anterior upper premolar (or milk molar?) the 

 anterior moiety of the crown is incompletely developed. 

 In the anterior lower premolar the anterior basal process, 

 which exists in aU the molars, is excessively developed, so that 

 the crown of the tooth assumes the bicrescentic pattern of 

 the Rhinoceros' lower grinder. This probably indicates 

 the manner in which the Tapiroid form of inferior molar 

 is converted into the Rhinocerotic, or Equine, form. 



The stomach is simple and oval, the cardiac and pyloric 

 orifices being closely approximated. The caecum is pro- 

 portionally smaller than in the Horse or Rhinoceros. There 

 is no gall-bladder. The heart is devoid of a septal bone 

 and of a Eustachian valve. There is only a single vena 

 cava anterior, and the aorta divides into an anterior and a 

 posterior trunk. There is no third bronchus. 'No distinct 

 scrotum is present. There are vesiculse seminales and 

 prostatic glands, but no Cowper's glands. The placentation 

 is diffuse. The teats are two, and inguinal. 



There are two or three species of Tapir at present living 

 in South America and one in South-west China, Malacca, 

 and Sumatra. The genus Tapirus has been found fossil in 

 Europe in rocks of miocene age. The closely allied extinct 

 genera Lopliiodon (and Coryphodon?) carry the Tapiridce 

 back through the eocene epoch. 



d. The Pal(Botheridce. — These are all extinct animals, the 

 remains of which are found in the older tertiary rocks; 

 and which are closely allied, on the one hand, with the 

 Horses and, on the other, with the Tapirs. 



The type of the family, Palceotherium, resembles the Tapir 



