THE TOXODONTIA. 829 



Berve to strain off from the contents of the paunch, and to 

 retain in store, a considerable quantity of water. 'I'he reticu- 

 lum is sharply defined from the rumen, and communicates with 

 it by a comparatively small aperture. The oesophageal groove 

 is bounded by only one ridge, which lies upon its left side. 

 The psalterium is reduced to a mere tubular passage, without 

 laminae; and the abomasum is large, and has the ordinary 

 structure. The pyloric end of the duodenum is considerably 

 dilated, and has been taken for a division of the stomach. The 

 caecum is short and simple. By a remarkable exception 

 among the Mammalia, the red blood-corpuscles are elliptical. 

 The foetal villi are scattered evenly over the chorion, so that 

 the placenta is diffuse. 



While the Tragulidm connect the typical Ruminants with 

 the non-ruminant Artiodaotyles, the Gamelidoe, on the other 

 hand, link them with Macrauchenia and the Perissodactyles. 



The Gamelidoe are at present represented by two very 

 distinct groups — the Camels of the Old World and the Llamas 

 of the New. They occur in the fossil state as far back as the 

 miocene epoch. 



II. The ToxoDONTiA. — This order has been founded for the 

 reception of the large extinct Mammal {Toxodon), remains 

 of which have been discovered in the later tertiary deposits 

 of South America. 



The supraoccipital surface of the massive skull slopes 

 obliquely upward and forward. There are supraorbital pro- 

 longations. The zygomata are very strong and arched, and 

 the bony palate is very long. 



In the upper jaw there are two small, inner, and two large, 

 outer, incisors. In the lower jaw there ure six incisors. In 

 the mandible there are canines in the middle of the interval 

 between the incisors and the grinders. In the upper jaw of 

 the adult, only indications of the former existence of alveoli 

 for canines remain. The grinding teeth are seven on each side 

 above, and six on each side below. They are greatly bowed 

 (whence the name of the genus), so as to be convex outward 

 and concave inward. They grow from persistent pulps, and 

 the enamel is absent upon their inner faces. 



The centra of the cervical vertebrae have flattened articular 

 faces. The dorso-lumbar vertebrae and the sacrum are not 

 known. The ribs are spongy internally, like those of ordinary 

 Mammals, not compact, as in the Sirenia. 



The scapula has a very large supraspinous fossa, as io 



