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Davenport. — Carotids of Alligator. 



EXPLANATION OF FIGURES 



ABBREVIATIONS. 



ao. Aorta. ad mu. lar. To muscles of larj'nx. 



art. pul. Pulmonary artery. mu. pet. Pectoral muscles. 



dt. Bot. Ductus Botalli. cc. (Esophagus. 



(id a. To oesophagus. tr. Trachea. 



n. Left arteria auonyma, Kathke = ventral distributmg trunk between IV. and 



III. arterial arches. 

 b. Right ditto. 



1. Arteria subvertebralis colli, Rathke = a. carotis dorsalis, Mackay = third arte- 



rial arcli and dorsal collecting trunk anterior to III. arch. In tliis vessel 

 three regions may be distinguished ; — 



I*. Left vessel of the posterior paired portion, the fellow of which on the right 

 side (!*') is usually lost, but in Figure 1 persists. 



1''-)- 1'''. Fused portion of \. (The leader should be continued to the vessel cov- 

 ered by tlie oesophagus in Fig. 1.) 



1°. Left vessel of anterior paired (unfused) portion. 



2. Left coilateralis colli, Rathke = a. carotis ventralis, Mackay = ventral distrib- 



uting trunk anterior to III. arch. 

 2'. Right ditto. 



3. Left a. subclavia = secondary or persistent subclavian (cf. Mackay). 

 * Anastomosing branch between 1" and 2 (=11. arterial arch ?). 



Fig. 1. Ventral aspect of head and neck regions of Alligator Mississippiensis, 

 28 cm. long. Part of the oesophagus and trachea are represented lying 

 above (ventral to) the median artery. 



Figs. 2 and 3. Lateral views of the arterial arches to show two cases of persistent 

 ductus Botalli. 



Fig. 4. Diagram, showing in side view the relation of the arterial arches of Croco- 

 dilia to the type. Heavy lines represent normal vessels; lighter lines, 

 abnormally occurring vessels ; dotted lines, vessels wholly absent in 

 adult. 



