46 ALLEN 



and third efferent branchial arteries on one side anastomose 

 with the corresponding trunks of the opposite side. From 

 either side of the ventral point of union of the first pair of effer- 

 ent vessels, a large hyoidean ariery (figs, i and 12, Hyo.A.) is 

 given off to the hyoid arch and mandibular region. The ven- 

 tral points of union of the second and third pairs of efferent 

 branchial arteries mark the source of the ventral artery (Pis. 

 I and II, figs. I and 12 ; Ven.A.) ; and \\\^ -pharynx artery (PI. 

 II, fig. 12 ; Phar.A.) may arise form either of the third efferent 

 branchial arteries. From the dorso-cephalic surface of the first 

 pair of efferent branchial vessels, the 2 common carotid arter- 

 ies (^\. I, figs. I and 5 ; C.Car.A.) are given off cephalad ; con- 

 tinuing dorso-caudad, the first efferent trunk unites with the 

 second to form \^% first or anterior epibranchial artery (PI. I, 

 fig. 5 ; Epbr.A.(i)), and in like manner the third and fourth 

 efferent branchial vessels unite to form the second or -posterior 

 ep ihr an chtal artery (PI. I, fig. 5 ; Epbr.A.,2,). The epibranch- 

 ial vessels on one side unite with the corresponding trunks on 

 the opposite side, forming a common chamber (PL I, fig. 5 ; 

 C.C.), which lies in a median line ventrad of the basi-occipital. 

 This chamber is the source of several large trunks ; the dorsal 

 aorta (PI. I, figs, i and 5 ; D.Ao.) arising from the left posterior 

 dorsal corner; the cceliaco-mesenteric (PI. I, figs, i and 5 ; Cce. 

 Mes.A.) below and to the right; and the common subclavian 

 trunk (PL I, fig 5) lies above the aorta and the coeliaco-mesen- 

 teric artery. In one case the subclavians were seen to arise 

 separately. The left one had its origin in the same place as 

 the common subclavian trunk, and the right one came from the 

 cceliaco-mesenteric artery. 



2. Arteries Arising From the Ventral Ends 0/ the Efferent 

 Branchial Arteries. 

 First under this head might be mentioned the 2 little hyo hyoid- 

 CMS inferior arteries (PL II, fig. 12 ; Hys.A.), which arise from 

 the cephalic surface of the first efferent branchial arteries just 

 before they unite ventrally. These vessels run cephalad a short 

 distance and then spread out laterad over the dorsal surface of 

 their respective muscles. 



