TRUE REPTILES. 211 
authentic cases are known of boas having attacked human 
beings. 
VaLvuE.—The oil of the large boas is much used for various pur- 
poses ; the skin is tanned, and made into boots, saddle-cloths, bags, etc. 
Allied are the ground fanged snakes. The Tree- 
Snakes (Dendrophide) have long, slender bodies, adapted 
for movement in the trees, and in many their rich green 
coloring affords them complete protection. They are 
tropical, and often found coiled up in birds’ nests, About. 
thirty-five species are known. The whip-snakes are allied 
forms. Fresh-Water Snakes (Homalopside).—In this 
family of fifty species are snakes that live more or less 
in fresh-water streams, and are found in all parts of the 
world, but especially in the East. The desert snakes are 
allied forms, and the curious Dasyfeltis, that lives upon 
eggs, swallowing them entire. 
In the Colubride represented by two hundred and sev- 
enty species, which include many of our American snakes, 
there are no rudimentary limbs. Both jaws are armed 
with teeth. The striped snakes, Zutenia, a common form 
in the Middle States, attain a length of two feet ; hiber- 
nating in holes or burrows during the winter, appearing in 
great numbers in early spring. They prey upon toads, 
frogs, and other small animals. The garter-snake is vivipa- 
rous, and often protects its young by receiving them into 
its mouth. They are extremely prolific, bearing at times 
seventy-eight young. The viviparous spotted spreading 
adder is even more remarkable in this respect, producing 
eighty-seven young at times. The hog-nosed snakes of 
North America have a short, thick body, with a large head. 
The black-snakes are a lustrous, metallic black, and attain 
a length of five feet. They are harmless, preying upon 
animals either in the trees or on the ground. The crack- 
whip snakes are incorrectly supposed by some to seize 
their tails in their mouths and roll along. 
