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Nostrils And Eyes Visible: When alligators and crocodiles move rapidly on land, they stand with their bodies raised so that they actually run along on their toes. When frightened or angered they can move with lightning speed and run so fast that a man cannot keep up with them.
In the water they lie submerged or nearly so with only the nostrils and eyes visible. When they completely submerge, valves close the nostrils, flaps cover and close the ears, and a valve in the throat closes the windpipe so the mouth may be opened to grasp food without water being taken into the lungs. When moving under water they hold their legs close to the body and swim by wiggling the entire body and propelling themselves with the tail.
The eyes of a spider are usually near the front or anterior end of the head, but some are directly on top. They are single facets, hence are called simple eyes. They may number two, four, six, or eight; eight is the usual number. However, the cave spiders lack eyes entirely. Regardless of the number, the eyes are always placed in a definite arrangement. Often some pairs are much larger than others.
The bones of cetaceans are spongy, the many small cavities within them being filled with oil. The skull is unusual in that its component bones do not abut one another end to end, but rather overlap broadly, making contact over a great area; presumably, this condition aids in withstanding the stresses caused by water pressure during forward movement. The jaws are not employed for chewing and are relatively weak. The nostrils are not located at the tip of the snout, but are situated atop the head. Two nostrils are present in the baleen whales; the toothed whales have only one. The eyes are small and located on the side of the head. External ears are wanting, and the openings of the auditory canals are minute. The lips are smooth and incapable of movement. |
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