190 



DR. P. CHALMERS MITCHELL ON THE 



mesentery which is luther more elongated in Ornithorhynchus 

 tlaan in Echidna. The middle mesentei'ic vein curves through 

 the mesentery, following Meckel's tract and giving off numerous 

 branches to the rather regular minor loops of the tract. The 

 ctBcum, which appears to be functionless, is placed very close to 

 the apex of the pendant loop ; so that nearly the whole of the 

 recurrent limb of the pendant loop is hind-gut. This is rather 

 ixxi unusual ariangement, but is present iu the Sloths among 

 Edentates and in the Mystacoceti amongst Cetaceans. Before 

 the recurrent limb reaches the dorsal line it is thrown into a 

 small bunch of minor loops forming an ansi coli dextra, less 

 numerous, however, than I figured for Echidna in my earlier 

 memoir, and placed much nearer to the dorsal middle line. 

 Then follows a point at which the hind-gut i-eaches the duodenal 

 region, to which it is attached by a secondary ligament. 



Text-fig'ure 3. 



Intestinal tract of JEchiclna Jii/strLv. 

 Lettering as in text-fig. 2. 



The rectal portion of the hind-gut is larger in calibre and is 

 thrown into very shallow minor loops. 



Sub-Class MARSUPIALIA. 



Order Marsupialia. 



Sub-Order Polyprotodontia. 



Family Notoryctidpe. Notorycies typhlops (text-fig, 4). 



The gut-pattern is extremely simple, showing a divergence 

 from the primitive condition by degeneration. There is no 

 distinction between the duodenum and Meckel's tract, the latter 

 being thrown into irregular minor loops ; there is no caecum, 



