Printed in Great Britain THE FUNCTION OF THE CONUS ARTERIOSUS IN THE PORT JACKSON SHARK, HETERODONTUS PORTUSJACKSONI

The conus arteriosus is a muscular chamber interposed between the ventricle and ventral aorta in Elasmobranchii, Holocephalii and the more primitive families of bony fish. Since Duverney (1702) suggested that it functioned as an extra ventricle, it has been variously regarded as an elastic reservoir to minimize pressure fluctuations (Keith, 1924; Daniel, 1934), an accessory pumping chamber (Gegenbaur, 1866, Stohr, 1876, Sudak, 1965), and a valvular structure to regulate the out-flow of bloo