A difference between the auricle and the ventricle of the mammalian heart is that the

The mammalian heart has four chambers - two atria (also called auricles) and two ventricles. One major difference between the auricles and the ventricles is that the walls of the ventricles are more muscular than those of the auricles. This is because the ventricles are responsible for pumping blood out of the heart and into the rest of the body, while the auricles receive blood returning to the heart. Additionally, the ventricles carry deoxygenated blood to the lungs or oxygenated blood to the rest of the body, while the auricles receive blood from the veins and have valves to prevent backflow. The ventricles also have outlets (arteries) that carry blood away from the heart, while the auricles do not.