In more specialized forms a posterior aorta passes backwards from the ventricle, as in Gastropods and the majority of Lamellibranchs.
In the primitive form a single anterior aorta is given off from the ventricle, the two together representing the dorsal blood-vessel of Chaetopods.
The dorsal vessel is prolonged anteriorly into an aorta, through which the blood is propelled into the great After Miall and Denny, The Cockroach, Lovell body-cavity or haemoReeve & Co.
T, Aorta, springing from the v, Stomach.
To the left of the vena cava is the Spigelian lobe, which lies in front of the bodies of the tenth and eleventh thoracic vertebrae, the lesser sac of peritoneum, diaphragm and thoracic aorta intervening.