402 



COMPARATIVE ANATOMY 



LJ7K 



l.posl.ci>rd> 



Si-v. 



FIG. 304. 



FIG. 305. 



Fit;. 304 HEART OF Protoji/t nt* nnnecttns. From the left side, part of the wall 

 of the left atrium being removed. (After Rose.) 



Co, conus arteriosus ; L.Vh and R.Vh, left and right atria; S.a, septum 

 atriorum ; Si. ?>, sinus venosus, within which the pulmonary vein (Lv) extends 

 to open into the left auricle by a valvular aperture ; W, fibrous cushion 

 extending into the ventricle. 



FIG. 305. Ceratodtisforsteri. DIAGRAMMATIC VIKW OF THE HEART AND MAIN 

 BLOOD VESSELS AS SEEN FROM THE VENTRAL SURFACE. (From Parker and 

 HaswelFs Zoology, after Baldwin Spencer. ) 



off". 1, 2, 3, 4, afferent branchial arteries ; 1 br, 2 br, 3 br, 4 br, position of gills ; 

 c.a, conus arteriosus ; d.a, dorsal aorta; d.c, ductus Cuvieri ; epi.l, epi.2, 

 epi.3, epiA, efferent branchial arteries ; hy.art, hyoidean artery ; i.v.c, post- 

 caval vein ; I. ant. car, left anterior caroiid artery ; l.aur, left auricle f.hr.r, 

 left brachial vein ; f.jtii/.r, left jugular vein; l.post.car, left posterior caro- 

 tid artery ; l.y>oxt.card, left posterior cardinal vein : J.pul.art, left pulmonary 

 artery; I sc. r, left sub-scapular vein ; r.mit car, right anterior carotid artery ; 

 r.rtur, right auricle ; r.ln-.r, right brachial vein ; r.jug., right jugular vein ; 

 i:i>oxt.<-ar, right posterior carotid ; r.piif.nrt, right pulmonary artery ; r.sr.r, 

 right subscapular vein ; mi/, ventricle. 



monary artery like the corresponding vessel in Crossoptf ry- 

 gians, arises from the fourth efferent branchial in Ceratodus 



