1891.] 



BOTALLI IN CERTAIN BIRDS. 



177 



Within the last few months I have come upon two cases of an 

 abnormality similar to the above, but still more marked, inasmuch 

 as instead of a cord a functional vessel was present. In the first 

 instance, which occurred in a Violaceous Night-Heron {Nycticorax 

 violaceus), the deviation from the ordinary arrangement was very 

 marked, as is well shown in the figure, which was drawn from the 

 injected specimen by Mr. Harrison, under my supervision. The 

 right carotid was very large at its origin, and ran for about an inch 

 towards the left (this portion of the vessel being marked in the 

 figure by an asterisk), when it turned almost at right angles 

 and ran forward in the usual manner, giving off at the turning 

 point the right vertebral, and a rather larger vessel which ran 

 back to join the dorsal aorta at the base of the heart. In the figure 

 the heart is removed, and the aorta pulled forward to show this 

 junction. Injection proved that this connecting duct had a lumen 

 and was thus quite functional, though apparently not of equal 



D.Ao 



Carotids of Nycticorax violaceus. 



C'rt, carotids ; F", vertebrals ; i),5, ductus botalli ; /«, innominates ; 



B.Ao, dorsal aorta. Tlie * marks the enlarged part of the right carotid. 



calibre throughout. The vertebrals {V, F), though given oif so far 

 apart, reached the spinal column at about the same point ; nor did 

 I observe any abnormality in the vessels of the left side. 

 Proc. Zool. Soc— 1891, No. XII. 12 



