the floor of its mouth as it distends and compresses its neck. Other methods 
of respiration are anal and pharangeal. 
Turtles are toothless, but their horny beaks with sharp cutting edges 
can inflict a nasty wound. It is just as well that the great majority are peace¬ 
ful by nature. Land turtles generally eat vegetable foods, whereas many 
aquatic forms eat animal and vegetable foods with equal relish. 
Female land turtles can do no more than hiss but the unmusical utter¬ 
ances of the males run the gamut from the pipings of the smaller species 
to the hoarse bellowings of the giant tortoises. 
Adult turtles vary greatly in size. The fresh-water mud turtle seldom 
reaches a size much larger than three inches in length. The trunk-back 
marine turtle is frequently over six feet long. 
The age achieved by some turtles is truly remarkable and Major 
Flower, who is an authority on the longevity of animals, writes: “Tortoises 
live to ages exceeding those of all other vertebrate animals.” 
Turtles reproduce by means of eggs laid in sand or loose earth. Even 
the sea turtles make for shore to lay their eggs. The eggs are round or 
elliptical and may be covered with a hard shell, stiffened by its content 
of calcium, or by a softer parchment-like covering. 
Alfred Sherwood Romer in Man and the Vertebrates pays a merited 
tribute to the turtle family. 
“The turtles are the most bizarre of reptilian groups. Because they are 
still living, turtles are commonplace objects to us; were they extinct their 
shells, the most remarkable armor ever assumed by a land animal, would 
be a cause for wonder. 
“The turtles, once within the shelter of their armor, became the con¬ 
servatives of the reptilian world. The oldest forms were contemporaries of 
the earliest dinosaurs. The ruling reptiles grew to dominate the reptilian 
scene but the turtles persisted unchanged. The dinosaurs passed away and 
the mammals took their place, but the turtles went calmly on their placid 
way. Now man dominates the scene, but the turtles are still with us. And 
if, in the far distant future, man in turn disappears from the earth, very 
likely there will still be found the turtle plodding stolidly on down the 
corridor of time.” 
Popularly classified, the following groups of turtles will be represented 
in this chapter: 
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