MUSEUM OF COMPARATIVE ZOOLOGY. 47 
In view of the interest attaching to this subject, I have thought it 
not wholly superfluous to put on record still another example of the 
persistence of the right root of the a. subvertebralis, — especially since 
so perfect a root from so old a specimen has not been heretofore men- 
tioned, and since no figure of this condition at any stage has, to my 
knowledge, been heretofore published. 
The specimen in question was one which was being used for study in 
the class in Vertebrate Anatomy by one of my pupils, Mr. H. O. Marcy. 
The Alligator was about 28 cm. long. The arteries had been injected 
from the heart, and a very evident branch, Figure 1, 1“, was shown, fully 
injected, running from the right common carotid, 6, to the a. subverte- 
bralis 1* + 1. Thus the whole carotid system had a very symmetrical 
aspect. The branch in question (1%), which must be regarded as the 
proximal end of the right dorsal carotid, was injected throughout its 
whole length. It measured 0.7 mm. in diameter, the corresponding 
measurement of the left root being 1.0 mm. The two trunks passed 
dorsally, encircling the trachea and cesophagus, and met near the median 
plane, dorsal to the csophagus and immediately beneath the vertebral 
column. 
I add also figures of two cases of persistent ductus Botalli, completing 
the VI. or pulmonary arch. Some trace of this condition appeared upon 
most of the individuals examined. In one case shown (Fig. 3), the in- 
jection filled only the dorsal and ventral ends of the ductus, the middle 
region remaining as a white cord. In the other case (Fig. 2), the pul- 
monary end only was injected. 
Finally, in a simple diagrammatic lateral view (Fig. 4), built up on 
the system of Rathke’s diagrams, as improved by Boas (’87), I have 
indicated the chief neck-arteries of the Crocodilia. In this diagram, 
the usually occurring arteries are drawn in heavy lines; those occurring 
less regularly or abnormally, in fine lines ; those absent, in dotted lines. 
I have introduced as the II. arch the anastomosis between 1* and 2 
(Fig. 1), thus adopting van Bemmelen’s (’88, p. 115) suggestion ; but 
I must repeat his caution, that this is only a rather probable, but by 
no means demonstrated homology. 
