Br.v, Branchial efferent vessel (vein).
They are said to be developed from the coelomic epithelium which covers the efferent vessel or its caeca.
D, The branchial efferent vessel carrying aerated blood to the auricle, and here interrupting the circlet of gill lamellae.
The afferent vessel of the' ctenidium receives blood from the vena cava or principal blood-sinus of the body, the efferent vessel opens into the auricle of its own side.
Ev, efferent vessel passing into ventral vessel (vv).
The oxygenated blood is carried from each gill by an efferent vessel on the external or pallial side of the axis to another longitudinal vessel which leads to the auricle on each side.