xm 



PHYLUM CHORDATA 



245 



artery (liy. art.} is connected with the most anterior of these. The 

 eight efferent vessels unite in pairs to form four epibranchial arteries 

 (epi.). The 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 



r.an2.ca> 



FIG. 920. Ceratodus forsteri. Diagrammatic view of the heart and main blood-vessels, 

 as seen from the ventral surface, aff. 1, 2, 3, 4, afferent vessels ; 1 br, 2 br, 3 br, 4 br, 

 position of gills ; c. a. conus arteriosus ; d. a. dorsal aorta ; d. c. precaval vein ; epi. 1, 

 epi. 2, epi. 3, epi. 4, epibranchial arteries ; hy. art. hyoidean artery ; i. v. c. postcaval vein ; 

 1. ant. car. left anterior carotid artery ; 1. aur. left auricle ; I. br. v. left brachial vein ; 

 /. jug. v. left jugular vein ; I. post. car. left posterior carotid artery ; I. post. card, left cardinal 

 vein ; 1. pul. art. left pulmonary artery ; I. sc. v. left subscapular vein ; r. ant. car. right 

 anterior carotid artery ; r. aur. right auricle ; r. br. v. right brachial vein ; r. jug. right 

 jugular vein ; r. post. car. right posterior carotid ; r. pul. art. .right pulmonary artery ; 

 r. sc. v. right subscapular vein ; vent, ventricle. (After Baldwin Spencer.) 



branches given off from the first epibranchial (I. 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 the last (fourth) epibranchial artery arises the pulmonary 

 artery (I. pul. art. and r. pul. art.), carrying blood to the lung. 



There are two precavals or ductus Cuvieri (d. c.), as in the Dog- 



VOL. II Q 



