INTESTINAL TRACT OF MAMMALS. 509 



Family Cebid^e. 



Sub-Family Nyctipithecinae. Callithrix cuprea (fig. 49, I, p. 521). 



There is no distinct duodenal loop. Meckel's tract is relatively not very long and 

 is composed of a simple series of loops at the periphery of an elongated expanse of 

 mesentery, the distal portion of which also acts as a mesocolon. The caecum is large 

 and capacious and of even calibre throughout. The hind-gut is very long and is 

 differentiated into a colic loop composed of a number of minor loops, a sigmoid 

 flexure, and a short straight rectum. 



The anterior mesenteric vein runs diametrically across the Meckelian mesentery, 

 receives a large colic vein, and is joined by the posterior mesenteric vein which drains 

 both rectum and colon. 



Sub-Family Pithecin^;. 

 I have examined no examples of this sub-family. The description given by Owen (19) 

 shows that the pattern of the gut is similar to that found in the Nyctipithecinae, with the 

 difference that Meckel's tract is relatively longer and the hind-gut relatively shorter. 

 The caecum is long and capacious. 



Sub-Family Mycetinju. Mycetes beelzebul (fig. 48, II, p. 520), M. seniculus. 

 There is no distinct duodenal loop. Meckel's tract is relatively short and composed 

 of a small number of simple minor loops. It is suspended along two-thirds of the 

 circumference of an oval expanse of mesentery, the distal one-third acting as a 

 mesocolon. The caecum is very short but extremely capacious, forming a bluntly 

 rounded cone, the base of which is nearly as wide as the height. The hind-gut 

 consists of a much distended proximal portion continuous with the caecum, a short 

 colic loop, and a relatively long rectum. There is no distinct sigmoid flexure and the 

 hind-gut as a whole is relatively shorter than in the Nyctipithecinae. The arrangement 

 of the mesenteric veins is much as in the last-named sub-family. 



Sub-Family Cebin^e. Ateles variegatus (fig. 43, p. 510), Cebus fatuellus, 

 Ouacaria rubicunda. 



In Ateles the duodenal loop (fig. 43) is rather wider in calibre than the succeeding 

 intestinal region, and the duodenum is more distinct than in most of the Platyrrhine 

 Monkeys. Meckel's tract is relatively rather long and is arranged in a series of closely- 

 set irregular loops at the periphery of an oval outgrowth of mesentery, the distal part 

 of which, as in many other Platyrrhines, acts as a mesocolon. The distal extremity of 

 Meckel's tract passes into the junction of the caecum and colon at an acute angle, and 

 in such a fashion as to suggest the vestigial presence of a second caecum. The caecum 

 is relatively short and forms a pointed elongated cone, which, in the fresh condition, 

 is slightly coiled. The hind-gut displays first an expanded region continuous with the 



vol. xvii. — pakt v. No. 10. — December, 1905. 3 T 



