1896.] INTESTINAL TBACT OP BIEDS. 153 



of the circular loop is expanded. In Pterodes it forms a long 

 narrow loop, the end of which is bent upon itself. The posterior 



Fig. 18. 



Fterocles bicinctus ; intestinal tract, x, Bhort-cirouiting vegsel divided. 



part of the circular loop remains in the primitive condition, and 

 has the long caeca attached to it. A short-circuiting vein from 

 the duodenum is present. The rectum is straight. 



In the ColumbsB which I have examined (Columbce of several 

 species, Phlogcenas cruenta) (fig. 19), it is tempting to regard the 



Fig. 19. 



Columba livia ; intestinal tract ; tbe spiral is figured as rather too symmetrical. 

 X, sbort-oirouiting Tesael divided. 



