Note 26 — SECTION VII. CLASSIFICATION OF ANIMALS AND PLANTS.

In Dipnoi, which are fishes with Amphibian characters, the paired fins have each a central segmented axis which bears on each side a series of radial pieces. The air bladder is a true lung, and is frequently used as such. The heart shows indications of becoming three chambered (two auricles and one ventricle). The left auricle contains arterial blood from the lungs. There is an inferior vena cava. The nasal sacs open posteriorly into the mouth.