1873.] 



CAROTID ARTERIES OF BIRDS. 



459 



pneumogastric nerve and jugular vein. Birds with this arrange- 

 ment may be termed aves bicurotidince abnormales (see fig. 3.) 



Fig. 3. 



Fig. 4. 



Fig. 3. Carotids at the base of the neck in aves bicarotidina abnormales, 

 Fig. 4. Carotids at the base of the neck in aves ccmjuneto-carotidinee. . 



Fourthly, the two carotids, running apparently as usual, directly 

 they meet, join and continue as a single trunk till near the head, where 

 the single vessel bifurcates, as in birds with a left carotid only. These 



Fig. 5. 



Fig. 6. 



Fig. 5. Carotids at the base of the neck in the genus Phcenicapferus, as found 

 by myself in all .specimens. 



Fig. 6. Carotids at the base of the neck in Cacatua sulphurca, according to 

 Meckel. 



may be termed aves conjuncto-carotidinee. In the common Bittern, 

 where this condition obtains, the arteries (fig. 4) are equal in size 

 or very nearly so ; but in the Flamingo (fig. 5) the left is extremely 

 small, and has been on this account overlooked by previous observers, 



