CLASS IV. AMPHIBIA. 
MORE OR LESS DISTINCTLY VERTEBRATED. WITH COLD RED BLOOD. HEART UNILOCULAR, OR 
WITH ONE AURICLE AND ONE VENTRICLE. EXTREMITIES FOUR, TWO OR NONE, OCCA- 
SIONALLY DISAPPEARING WITH AGE. SKIN NAKED, DESTITUTE OF SCALES. RIBS SHORT OR 
WANTING. RESPIRATION BY GILLS OR LUNGS, OR BOTH CO-EXISTENT. FORM IN SOME FAMI- 
LIES UNDERGOES A COMPLETE METAMORPHOSIS. AQUATIC OR TERRESTRIAL. CARNIVOROUS. 
EGGS IMPREGNATED AFTER EXCLUSION. 
The Amphibia or Amphibians have, until recently, been treated as an order of Reptiles ; 
but they present so many and such important variations from the character assigned to that 
class, that modern naturalists have almost unanimously agreed to consider them a distinct class, 
forming a group allied on the one hand to the Reptiles by the C@cilid@, and on the other to 
the Fishes by the Szrenide. 
As early as 1816, De Blainville published a system of classification, which he had publicly 
taught in his lectures for several years previous. In this he indicated the propriety of sepa- 
rating the animals under consideration from the Reptiles. Of these he made a class, which 
he designated as Nudipelliféres or Ichthyoides nuds. This he divided into four orders: 1. 
Batraciens, Frogs; 2. Pseudosauriens, or Salamanders ; 3. Amphibiens, as Proteus, Siren, 
&c.; 4. Pseudophydiens, as Cecilia. This was afterwards modified and enlarged in his 
“Principes d’Anatomie Comparée,” published in 1822, when he designated his third class 
under the name of Subichthyens. 
The characters assigned to this class must be taken with some limitations. Some of the 
genera undergo no metamorphosis whatsoever, either in form or respiration; at least none 
has hitherto been observed. Nor is the phrase “ unilocular heart” literally exact ; for although 
the auricle is externally single, yet dissections have proved that internally itis in some genera 
separated into two distinct auricles. 
The Amphibians present such a variety of changes, and such modifications of structure, as 
to have given rise to many systematic arrangements. From the various systems proposed, 
we select that of Mr. Bell, as detailed in his admirable work on the British Reptiles, with 
such modifications as are necessary to produce uniformity with the general plan of this 
Report. 
