480 DK. P. CHALMEES MITCHELL ON THE 



extremely capacious colic loop and a wide, sacculated, but nearly straight rectal 

 portion. The arrangement of the veins is essentially identical with that found 

 in the Tapir. 



Family Equid^e. Equus granti (fig. 25, p. 479). 



I have examined the intestines of several Horses and Asses, but, except in minor 

 details, the pattern displayed is identical. The duodenum is not so well marked as in 

 the Tapir, but is more specialised than in the Rhinoceros. Meckel's tract is relatively 

 longer than in the two other Perissodactyle families, and consists of a number of 

 regularly arranged minor loops round the circumference of an oval expanse of 

 mesentery, united with the general mesentery only by a narrow neck. The esecum 

 is very long and capacious. The hind-gut displays an enormously capacious colic 

 loop exactly similar in its relations to that of the Tapir and Rhinoceros, and a 

 relatively long and slightly folded rectum. The arrangement of the mesenteric veins 

 is similar to that in the other Perissodactyles, save that the anterior mesenteric 

 vein is made up of a number of branching factors. 



The almost essential similarity of the gut-pattern displayed by the three Perissodactyle 

 families, although the members of these differ much in structure and habits, is very 

 striking. Except so far as both Artiodactyles and Perissodactyles have the whole gut 

 relatively long and the hind-gut especially long, there is no special connection between 

 the patterns displayed by Artiodactyles and Perissodactyles. In the former group the 

 lengthening of the proximal portion of the hind-gut assumes the form of a narrow and 

 very long loop with no trace of spiral coiling ; in the latter the colic loop is always 

 coiled and relatively narrower. 



Order RODENTIA. 



Sub-Order SIMPLICIDENTATA. 

 Group Haplodontoidea. 

 I have had no opportunity of examining members of this group. 



Group Sciueoidea. Xerus capensis (fig. 26). 

 This animal shows the characteristic Rodent configuration of the alimentary canal 

 in a relatively simple form. There is a fairly distinct duodenal loop. Meckel's tract 

 consists of a number of simple minor loops at the periphery of the usual, nearly 

 circular expanse of meseutery, and terminates in a relatively straight recurrent portion 

 Avhich enters the caecum at right angles. The caecum in Xerus is a very capacious 

 sac, much expanded distad of the small intestine and tapering to a point anteriorly. 

 The hind-gut is divided into two regions. There is a much lengthened colic portion, 

 variously disposed, but never showing any trace of the spiral coil which is so well 

 marked in the Artiodactyles ; in Xerus this portion consists of two specialised loops 



