AMPHIBIANS AND REPTILES. 35 
Class Amphibia. 
The Amphibians. 
Coracoid element of scapular arch distinct and with quadrate 
bone. Limbs consist of a single proximal element, 2 propodials 
(sometimes united), a carpus and tarsus, metapodials and pha- 
langes. Cartilage of basis-cranii unossified usually, and sup- 
ported by parasphenoid. Vertebral column consisting entirely 
or in part of intercentra. Stapes present. Cerebellum small. 
Mesencephalon smaller than prosencephalon or hemispheres, and 
latter with ventricles on inner side of their principal mass. Heart 
with 3 chambers, 2 auricles and a ventricle. On each side of 
heart 3 or 4 aorta bows. Lungs always present. Gall-bladder 
and urinary-bladder present. Oviducts: entirely distinct, and 
opening by fontanels into abdominal cavity at a distance from 
ovaries. Reproductive, renal and digestive products discharged 
into a cloaca. Male without distinct intromittant organ. 
Cold-blooded vertebrates, intermediate between fishes and rep- 
tiles. ‘They differ from fishes chiefly in the absence of rayed fins, ° 
the limbs being usually developed and functional with the skeletal 
elements of the limbs of reptiles, and in the reduction or absence 
of the various bones of the branchial, opercular and suspensory 
systems. Amphibians have a more or less complete metamor- 
phosis. The young, or tadpoles, are fish-like, more or less 
aquatic, and breathing by means of external gills. These differ 
from the gills of fishes in standing on fleshy processes of the 
branchial bones, and not on the bones themselves. The tadpole’s 
tail is provided with a more or less distinct fin-like membrane, 
usually disappearing with age. Later lungs develop, and in most 
cases the gills disappear. Skin mostly naked and moist, used to 
some extent as an organ of respiration. Reproduction by means 
of eggs, which are of comparative small size and without hard 
shell. They are deposited in or about the water. Rarely are 
the young born alive. 
Key to the orders. 
a. Body elongate, with tail always distinct; hind limbs not especially en- 
larged. URODELA 
aa. Body short, depressed; tail disappearing with age; hind limbs much en- 
larged. SALIENTIA 
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