SORTING OF ANIMALS 9 
lizards, rudimentary limbs are observed. The tortoises 
and crocodiles have limbs fully developed. A peculiarity 
of reptiles is the shedding of the 
teeth ; but new ones form as fast 
as the old ones drop out. 
CROCODILE The reptiles are enormous and 
swallow their prey whole. Serpents, 
as a general rule, affect moist places 
in the neighborhood of water, although some are inhabitants of dry 
sandy deserts. Lizards, for the most part, live in sandy portions of 
hot and tropical regions. They either burrow in the ground or live 
in holes of trees or walls. The largest kinds of reptiles are found 
in the warmer parts of the globe. 
14. Birds.—The step between reptiles and birds is not 
as great as it may seem. The earliest forms of birds had 
teeth in their jaws and possessed jointed 
tails. The reptiles of early times were 
able to fly. Some birds have claws on 
their wings, and these suggest another 
purpose than for use in flying. Birds are 
warm blooded, more so than any other 
of the vertebrates. All the other ani- 
mals below them are cold blooded. Rep- ‘this ancient bird 
tiles are considered ugly; but birds, as a lived ages, and ages 
ago. It had teeth and a 
-y_ long tail, like reptiles, 
rule, are noted for beauty and adorn- ied or the nosy 
fs s : a jq_ beak and rudimentary 
ment. Their feathers give birds a dis- (sk apt sudimentary 
tinction that applies to every variety pies. ty eelenttate 
: Archaeopteryx, was a 
and species. little larger ” than a 
15. Mammals.—Animals that suckle “” 
their young and produce them at birth were formerly 
considered set off to themselves. No connecting link had 
been observed between them and animals that lay eggs, 
*such as birds and reptiles. Yet it is now known that 
the lowest form of mammals does lay eggs. This is 
the duck mole, that lives on and burrows in the banks 
OLDEST KNOWN BirpD 
