| Each posterior spiracle has three openings or slits arranged parallel or converging, on a sclerotized plate. |
| H are seen the long filiform external gills which now project out from all the visceral clefts, including the spiracle. |
| The plastron is actually a modified air storage chamber that consists of air in a series of cuticular grooves radiating from a spiracle. |
| In common usage the hyomandibular cleft is called the spiracle, and the series of clefts behind it the branchial clefts. |
| In many sharks and in sturgeons the spiracle forms a conspicuous opening just behind the eye. |
| The nasal opening of whales and other cetaceans is called a spiracle, as is the respiratory opening behind the eyes of rays and skates. |
