SKELETON. 
;6i 
contain more elements. The palatines and vomer, and more rarely the parasphenoid, 
may be armed with teeth, like the upper jaw; but in the frogs and toads the lower 
jaw is very generally toothless. In all cases the teeth are small, simple, and pointed ; 
being adapted for holding, and not for masticating. The shoulder-girdle, which is 
largely cartilaginous, is placed 
very close to the head, and com¬ 
prises the usual elements. Each 
scapula, or shoulder-blade, has an 
upper cartilaginous portion, ex¬ 
tending inwards nearly to the 
middle line of the back; while in 
the frogs each metacoracoid has 
an inward cartilaginous expan¬ 
sion, which may either meet or 
overlap its fellow, and is of much 
importance in classification. In 
advance of the metacoracoids is 
another pair of transverse bars 
commonly known as the precora¬ 
coids ; while in front of these is a 
single median rod termed the omosternum; the proper sternum, or breast-bone, 
occupying a similar position behind the metacoracoids. In the fore-limb the radius 
and ulna may be united, and the wrist cartilaginous; the number of toes among 
living forms never exceeding four, and being sometimes reduced to three. More 
variation exists in the hind-foot, the number of toes in the long-tailed forms 
ranging from two to four, whereas in the frogs and toads it is always five. Only 
in a few frogs and newts are the toes furnished with claw-like nails; in the 
greater number of forms these being naked, although often connected by webs, and 
sometimes carrying adhesive discs on the lower surface. 
In all Amphibians the brain is of a very low type, its component 
portions lying in a line one behind the other, without overlapping. 
All possess the three chief organs of sense, although in some instances the eyes 
may be very minute and covered with an opaque skin. In frogs and toads the 
eye is large and very highly developed; generally possessing two lids, of which the 
lower one is larger and thinner than the upper, and more or less transparent. 
Greater variation exists in the structure of the ear, which is simplest in the 
tailed forms. The nose opens externally in a pair of nostrils situated near the 
muzzle, and by another pair of apertures into the mouth; the latter character 
distinguishing Amphibians from the majority of Fishes. The tongue, which acts 
only in the very slightest degree as an organ of taste, and is wanting in one group 
of frogs, is generally well-developed and thick, filling the whole space between the 
jaws, and being capable of a large amount of motion; it differs essentially from 
that of the hig her Vertebrates in that it is affixed to the inner side of the front of 
the lower jaw, with its tip pointing down the throat. 
All Amphibians lay eggs, which are generally although not 
invariably deposited in fresh water, and fertilised as they are 
Soft Parts. 
Development. 
