Rescuing Turtle From Railroad Tracks

The rigid shell means turtles cannot breathe as other reptiles do, by changing the volume of their chest cavity via expansion and contraction of the ribs. Instead, turtles breathe in two ways. First, they employ buccal pumping, pulling air into their mouth then pushing it into the lungs via oscillations of the floor of the throat. Secondly, by contracting the abdominal muscles that cover the posterior opening of the shell, the internal volume of the shell increases, drawing air into the lungs, allowing these muscles to function in much the same way as the mammalian diaphragm.
The shape of the shell gives helpful clues to how the turtle lives. Most tortoises have a large dome-shaped shell that makes it difficult for predators to crush the shell between their jaws. One of the few exceptions is the African pancake tortoise, which has a flat, flexible shell that allows it to hide in rock crevices. Most aquatic turtles have flat, streamlined shells which aid in swimming and diving. American snapping turtles and musk turtles have small, cross-shaped plastrons that give them more efficient leg movement for walking along the bottom of ponds and streams.
The color of a turtle's shell may vary. Shells are commonly colored brown, black, or olive green. In some species, shells may have red, orange, yellow, or grey markings and these markings are often spots, lines, or irregular blotches. One of the most colorful turtles is the eastern painted turtle which includes a yellow plastron and a black or olive shell with red markings around the rim.
Tortoises, being land-based, have rather heavy shells. In contrast, aquatic and soft-shelled turtles have lighter shells that help them avoid sinking in water and swim faster with more agility. These lighter shells have large spaces called fontanelles between the shell bones. The shells of leatherback turtles are extremely light because they lack scutes and contain many fontanelles.