1. The first of these types is encountered in the Old World cynomorphous monkeys. In all of these animals the caecal pouch is wide but comparatively short, of nearly uniform caliber and sacculated like the rest of the colon, of which it forms the direct caudal continuation (Fig. 465, _III_, _C_, 1). The terminal portion of the pouch is usually blunt, globular and rounded (Figs. 428, 430 and 431), in a comparatively small number of forms slightly pointed (Figs. 427 and 437). 2. In the second group the terminal reduced portion persists either as a fairly distinct appendage, or in the form of a tapering pointed extremity into which the caecal pouch proper is continued (Fig. 465, _III_, _C_, 2). This type is encountered in certain non-ruminant Ungulates. An example of the first condition is furnished by the caecal apparatus of the peccary (_Dicotyles torquatus_) (Fig. 370), while the structures in _Tapirus americanus_ (Fig. 377) illustrate the second form. =IV. Caecal Apparatus Combined with Structural Modifications of the Proximal Colon of Similar Physiological Significance. (Fig. 465, IV.)= The fourth general mammalian group comprises forms in which the caecal pouch is large, with or without terminal appendage, while in addition the large intestine develops structural modifications which possess the general functional significance of the caecal apparatus. This highly developed and complicated structure of the alimentary canal indicates that the habitual food of these animals is bulky and difficult of digestion. Accordingly we find the group composed in main of the majority of the Ungulates and Rodents (with the exception of _Myoxus_), forms in which the diet under natural conditions is purely herbivorous. Other mammalian orders, however, also furnish representatives of this type of caecal apparatus, the conditions as regards character and quantity of food habitually taken corresponding to those encountered among the Ungulates and Rodents. Thus the _Phalangers_ among Marsupials (Fig. 352), _Galeopithecus_ (Fig. 419) as an exceptional form among the Insectivora, and certain lemurs among Primates (Figs. 420-425) present examples of a highly developed and specialized type of caecal apparatus. The intestinal tract of these forms must therefore be considered from two points of view: I. The caecum proper. II. The analogous structural modifications of the proximal segment of the colon. =I. CAECUM PROPER.= The pouch of the Ungulates and Rodents, taking these forms as the typical representatives of the entire group, is usually of very large size compared with the rest of the alimentary canal. Two types are found: