REPTILES. 193 
Turtle, and with these the animal moves rapidly through 
the water, they being a pair of aquatic wings. On land, 
Fig. 157.—Gvreen Turile. 
their walk is an awkward shuffle with these flippers. 
They are very convenient instruments, however, in scoop- 
ing out holes in the sand for their eggs. Nearly two 
hundred eggs are laid in one nest. When laid, they are 
covered up with the sand. The white of these eggs, 
which are highly prized, does not harden in boiling. The 
Green Turtle, the flesh of which is considered so great a 
luxury, is common on the shores of most of the islands 
of the East and West Indies. It has been known to 
reach a weight of five or six hundred pounds. The tor- 
toise-shell of commerce comes from the Hawksbill Tur- 
tle. In this animal the horny plates are large, and are 
arranged like shingles on a roof. 
319. Of the second order of Reptiles, the Crocodiles, 
there are two groups—the true Crocodiles, common to 
both hemispheres, but most abundant in the Nile and 
other African rivers, and in the Ganges; and the Alliga- 
tors, which are confined to America. There is not any 
very great difference between them ; but the Crocodiles 
are more thoroughly aquatic than the Alligators, and 
