Here also the blood system has no communication with the sinus system of the coelom.
The aim is not self-destruction, but self-preservation; and yet the ethics of Manichaeism appears in point of fact as thoroughly ascetic. The Manichaean had, above all, to refrain from sensual enjoyment, shutting himself up against it by three seals - the signaculum oris, manus and sinus.
Veneridae.-Foot well developed; pallial sinus shallow or absent.
When it is slit open from in front a longitudinal ridge is seen in its posterior wall, which is called the verumontanum or crista urethra, and on each side of this is a longitudinal depression, the prostatic sinus, into which numerous ducts of the prostate open, though some of them open on to the antero-lateral surface.
The aorta is not independent as in Chitons, but is a sinus like the other channels of the circulation.