' The extremely different characters of the adult B. suggest the idea of an arresting of the metamorphosis at different stages; but whilst this idea may be helpful to our under standing of the close affinities which really pervade the whole order, it must be remem bered that it does not equally apply to all parts of the animal system; and that even as to those which have been particularly mentioned in the brief account above given of the metamorphosis of the IL, some in their perfect state appear to have one part in what, for convenience, may be termed a more advanced slate than another; whilst all are adapted with equal perfection to the situations in which they are appointed to live, both with reference to the wants of their own existence and the preservation of that of their species.
If the limbs of the tadpole or the frog are injured or destroyed during their growth, the loss is wonderfully repaired. This power of reproducing lost limbs continues to be possessed in an extraordinary degree by the adult newt (q.v.).
B. are generally inhabitants of warm or temperate climates. Those which inhabit temperate climates generally become torpid during winter. They are either almost entirely aquatic or are found in moist situations. The British species are very few. In some of the Scottish isles they are unknown.
B. are commonly divided into two sub-orders—eaducibranchinta, in which the gills (lrandria) disappear (are caducous), and perennibranchiata, in which they are persistent (perennial). The perennibranehiate Batrachia are comparatively few. Axolotl, siren, and proteus are examples. The caducibranehiate Batrachia are subdivided into tailless or avourons, as frogs, toads, etc.; and tailed, as newts, salamanders, etc. Some of the frogs and toads of warm climates are much larger than those of Britain; but the largest known B. are the sieboldia maxima of Japan, and protonopsis horrida of the Ohio (vari
ously styled hellbender, mud devil. ground puppy, young alligator, and fish salamander), both creatures of the newt or salamander form, the latter of which is 2 ft. long, and the former is of still greater size.
Fossil remains and footprints in rock attest the existence, in former geological periods, of B. of large size. "It is only in tertiary and post-tertiary strata that extinct species referrable to still existing genera or families of this order have been found." These occur both of the tailed and tailless forms. One of them has been a subject of particular interest, because its remains, when first discovered by Scheuchzer, in the beginning of the 18th c., were mistaken for the remains of a human being, and the discoverer enthusiastically urged them upon the attention ofilis contemporaries as a proof of the deluge. To this salamandroid fossil the name andrias (from the Gr. for man) sekenelaeri has been given.--Footmarks in the sandstones and shales of the coal-measures in Pennsylvania seem toThave belonged to B. resembling frogs or toads, but of great size, some of the footprints being 2 in. in diameter, and a breadth of nearly 4 in. between the right and left footprints.—Some of the older batrachian fossils differ so widely from all existing types that new sub-orders have been formed for them. Those of the suborder which arehegosaurus (q.v.) is the best known—are remarkable for having the head covered with bony plates; those of the order labyrintho dontia, for the labyrinthic structure exhibited in the transverse section of the teeth.
See LATIYRINTIIODON.