156 MR, P. CHALMERS MITCHELL 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 Psittaci 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. 
CoRACIIFORMES. 
Of the birds in this group that I have examined, the Owls (fig. 22) 
and Caprimulgide 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. 
Bubo 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 ceca 
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 ceca. Those without 
functional cwca display very simple divergences from the common 
