No class varies more greatly in the size of its representatives. We find tiny chameleons and lizards but a very few inches long, and great crocodiles many feet in length. There are snakes no longer than one’s little finger, and boa-constrictors large enough to swallow a man or a cow. There are little turtles of the diameter of a twenty-five-cent piece, and huge turtles that weigh eight hundred pounds. When we name these species we are reminded what a wide variety there is in the families of the reptilian class. There are four methods of securing safety, or life-preservation, known among the reptiles; the most common,--because the small creatures to which it pertains are happily the most numerous of their group--is imitation in form and color. We have noted this in the lizards. The second method is the wearing of natural armor, by the thickening of the skin or hide. Thus, in the serpents, the skin is often covered with scales; the scale-plate of crocodiles and alligators is generally bullet-proof; in the turtle family the body is protected by a hard, solid box of united plates neatly and closely put together. A third means of preservation is found in weapons of defence, as great teeth and huge, lashing tails, as in the crocodilia; or violent poison in fangs, as in many snakes. Lastly, the greater reptiles have often no weapon but their vast strength, as most of the boas; no creature desires to cope with them or go within reach of their mighty coils. To make closer acquaintance with the most prominent and notable of all reptiles, we must go to the torrid zone. The hot breath of the desert smites us, as the sun’s rays are like fierce thrusts, the noon-day is scorching, still, breathless; the green of summer seems to have been burned away, as in a furnace blast. There, stretched his lazy length on the black ooze, beside the famous river of Africa, lying in the full glare of the sun, his little eyes sleepily shut, heedless alike of the insects that cluster about him, and of the birds which dart down to carry them off, lies the monster that was in ancient times often worshipped as a god--the crocodile. The crocodile gives his name to his order, crocodilia; which order, happily for human convenience, has but few representatives. The characteristics of this order are: aquatic habits, firmly planted teeth, skin thick and furnished with armor-plates, a long tail, four short legs, and feet with toes. The crocodile’s limbs are muscular and active, well articulated or put together, and end in fingers or toes, whichever we may choose to call them. The strong, bony plates are chiefly on the creature’s back. A peculiarity of the teeth is that they are cone or wedge shaped, and a pair on the lower jaw are much longer than the others, and fit into notches in the upper jaw when the mouth is closed. What is the use of these big teeth? It is to seize and hold firmly the prey of the monster, so that by no struggles can it escape when held by these cruel prongs.