There are likewise two pulmonary veins, entering the left atrium by one orifice.
The sides of the atrium are unfortunately occupied by plain ungainly buildings five storeys in height, awkwardly accommodating themselves to the upward slope of the ground.
The pharynx projects freely into the atrium; it is surrounded at the sides and below by the continuous atrial cavity, but dorsally it is held in position in two ways.
At the same time, blood in the lungs goes to the left atrium, the left ventricle, but then back to the lungs rather than going to the body because the pulmonary artery is connected to the left ventricle.
Spermatheca rarely with diverticula; sperm ducts as a rule occupying two segments only, usually opening by means of an atrium.