252 



ZOOLOGY 



SECT, 



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

 said to exist. Each branchial arch has two efferent branchial 

 arteries. A hyoid artery {hy. art.) is connected dorsally and veat- 

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

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



ofLc 



rrpost.cetr 



it-car Lantjiar 



r.anl^an 



Fig. 909. — Ceratodus forsteri. Diagrammatic view of the heart and main blood-vessels, 

 .as seen from the ventral surface. a^\ 1, 2, 3, 4, afferent vessels ; 1 6r, 2 &?', 3 hv^ 4 bi\ position of 

 gills ; c. a. conus arteriosus ; d. a. dorsal aorta ; d. c. precaval vein ; epL 1, ejyi. 2, e-pi. 3, ejse. 4, 

 epibranchial arteries ; hy. art. hyoidean artery ; i. v. c. postcaval vein ; I. ant. em: left 

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

 vein ; /. pout. car. left posterior carotid artery ; (. po-^t. card, left cardinal vein ; t. put art. 

 left pulmonary artery ; I. .fc v. left subscapular vein ; r. ant. car. right anterior carotid 

 artery; r. aw: right auricle; r. br. v. right brachial vein; r. jug. right jugular vein; 

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

 subscapular vein ; vent, 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 carotid branches 

 given off from the first epibranchial (1. post. car. and r.post. car), 

 and from the hyoidean arteries {I. ant. car. and r. ant. car), and 

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



