252 



ZOOLOGY 



SR(.'T. 



in front of tlie conns, so that a ventral aorta can hardly be 

 said to exist. Each branchial arch has two efferent branchial 

 arteries. A hyoid artery (Jiy. art.) is connected dorsally and vent- 

 rally with the most anterior of these. The eight efferent vessels 

 unite in pairs to form four epibranchial arteries (epi.). The 



rpost.cctr 



l.postcar l.oTit^ar 



rci/it.car. 





r.scv 



sc/i/ 



Lpost-cctrd 



i.-v.c 



d-a 



Fio. 009.— Ceratodus forsteri. Diiigranimatic view of the heart and main blood-vessels, 

 as seen from the ventral surface, aff. 1, 2, 3, 4, afferent vessels ; 1 Ui-, 2 hr, 3 hi\ 4 6r, position of 

 gills ; c. (I. I'onus arteriosus ; (/. a. dorsal aorta ; d. c precaval vein ; tpi. I, epi. 2, epL 3, epi. 4, 

 epibranchial arteries ; hi/, art. hj-oidean artery ; i. v. e. postcaval vein ; /. (Uit. air. left 

 anterior carotid artery ; I. aur. left auricle ; I. In: v. left brachial vein ; I. jug. r. left jugular 

 vein; I. po.^l. rar. left posterior carotid artery; I . post . rard. left cardinal vein; I. put art. 

 left ]inlnionary artery ; /. .w. r. left subscapular vein ; r. ant. car. right anterior carotid 

 artery ; r, aur. right auricle ; ;•. tir. r. right brachial vein ; }•. jug. right jugular vein ; 

 r. post. rar. right posterior carotid; r. put. art. right pulmonary artery; r. sc. r. right 

 .subscapular vein ; rent, ventricle. (After Baldwin Spencer.) 



latter unite dorsally to form a main trunk, which combines with 

 the corresponding trunk of the opposite side to form the median 

 dorsal aorta {d. a.). The head is supplied by carutid branches 

 given off from the first epibrancliial (/. p)od. car. and r. post, cay;), 

 and from the hyoidean arteries (/. ant. car. and r. ant. car), and 

 the latter also gives off a lingual artery to the tongue. From 



