1. The pneumostome lung cavity is heavily vascularized to allow gas exchange. 2. Banana slugs have a single lung which opens externally via a pneumostome . 3. The pneumostome opens and closes in a cyclical manner. 4. These groups lack a pneumostome , having a much larger opening to the cavity. 5. Banana slugs have a single lung ( on the right side ) which opens externally via a pneumostome . 6. The placement of the pneumostome on the mantle helps to distinguish the species of " Ariolimax ". 7. Air enters through the pneumostome into the animal's single lung, the air-filled mantle cavity. 8. There are two light brown bands on the dorsum and mantle, the right band passes above the pneumostome . 9. Dark lateral bands run relatively deeply at the sides and the pneumostome is usually enclosed by right-side band. 10. However, the position of the pneumostome is often not at all easy to discern when this orifice is completely closed.
