230 



DE. P. CHALMERS MITCHELL ON THE 



LA RI. 



LARIDJE. I have already described and figured the conformation of the gut in Larus 

 marinus (26. fig. 17). The duodenum is narrow and straight. Meckel's tract is thrown 

 into a series of irregular loops, the first of which prohably represents " ," while " b " 

 appears as a number of closely-set short loops, proximad of the diverticulum. " c " and 

 the large supra-duodenal loop are both present. The caeca are vestigial, and the rectum 



Fig. 56. 



Intestinal Tract of Sterna hirundo. 



is rather long. Other specimens of Larus marinus were identical, except that Meckel's 

 diverticulum was absent, a condition frequent in the Gulls. Larus argentatus was 

 closely similar, and L. ridibundus differed only in that the loops of Meckel's tract were 

 more definite and were twisted into a common spiral. In Pagophila eburnea (fig. 54, 

 p. 234) the general conformation is similar. Loop "c" and the supra-duodenal fold are both 



