AMPHIBIOUS VERTEBRATES. 195 
Class 1V.AMPHIBIOUS VERTEBRATES. SALAMAN- 
DERS, TOADS, etc. (Batrachia). 
General Characteristics——The Batrachians are amphibi- 
ous Vertebrates that breathe air by perfect lungs, though 
some adult forms have gills. They pass through a distinct 
metamorphosis. The higher forms have paired limbs, the 
toes not being clawed as in the reptiles. They are gen- 
erally oviparous. . 
Skeleton.—In the frog the skull is closely connected 
with the body, and differs from that of higher Vertebrates 
in being partly cartilaginous 
(Fig. 237). The bones of the 
limbs, when present, resemble 
those of higher Vertebrates. 
\ Tarsus. 
( Metatarsus, 
‘ Phalanges. 
FIG. 237.—Skull of the frog, (Rana 
esculenta), from below, showing 
teeth and the cartilaginous gir- 
dle-bone, y. 
Fic. 238.—Bones of the right 
leg of a young toad, greatly 
This is shown in Fig. 238, enlarged. The femur not 
E shown; the tibia and fibula 
which should be compared are combined together. (Af- 
with the limb of the cat. ter Morse.) 
Digestion—The mouth is 
generally large, and in the frog (Fig. 237) the upper jaws 
are armed with delicate, saw-like teeth. Tadpoles have 
