38 



SCYLLIUM 



5. Ventral view of heart and great vessels as exposed by a cut in the middle ventral line from the mouth 

 to the pericardium : sinus venosus ; auricle ; ventricle ; conus arteriosus ; hepatic sinus ; posterior cardinal sinus ; 

 anterior cardinal sinus; ductus Cuvieri; ventral aorta; afferent branchial vessels; thyroid gland; pericardio- 

 peritoneal opening; gill clefts and gills. 



