156 ME. p. OHALMBBS MITOHELl ON THE [Jan. 14, 



to that of the Accipitres ; but this, I think, is superficial, and merely 

 due to the relation to the common type. The marked features of the 

 divergence from type in the Psittaei consist in the elongation of a 

 definite number of loops and in the matting of these loops together, 

 the loops being folded over each other backward and forward. 

 There is no trace of the formation of a loop supplied by the pos- 

 terior mesenteric vessel, which is the most striking Accipitrine 

 character. 



COBAOIIFOBMES. 



Of the birds in this group that I have examined, the Owls (fig. 22) 

 and CaprimulgidBB are the most primitive, and indeed differ very 

 little from the primitive type. The duodenal loop, as in other 

 Coraciiform birds, is very wide, especially towards its extremity. 

 The circular loop of the gut remains in nearly the primitive con- 

 Fig. 22. 



Siibo maximus ; intestinal tract. 



dition, being thrown into a series of short convoluted lobes, 

 supplied by radiating branches from the middle mesenteric vein. 

 In Bubo maximus, where the gut is relatively short, the only 

 subsidiary loop of the mid-gut series that is prominent is the 

 distal loop, along which, as in the common type, the large caeca 

 run forward. In other Owls there is frequently another well- 

 developed subsidiary loop on the part of the mid-gut between the 

 duodenum and the vestige of the yolk-duct. The rectum is 

 straight. The three branches of the portal vein, the duodenal, 

 median, and posterior mesenteric veins, all are in the typical 

 condition. I have not been able to see many of the other 

 birds in this group which possess long coeca. Those without 

 functional caeca display very simple divergences from the common 



