Batrachia, Batrachians

AMPHIBIA, n. pl. (Zool.) A cla of animals which were long confounded with reptilia. When young, they breathe by branch iæ, or gills, and resemble fishes in the general conformation of the body; but they change their forms and acquire lungs before becoming adult. Like fishes and reptiles, they are cold-blooded animals, their circulation is incomplete, and their respiration comparatively inactive. The skin is naked or unarmed, the skeleton very incemplete, and the heart is composed of a single ventricle and two auricles. In their external form they vary considerably, some resembling lizards, and even serpents, but generally the body is flat, short, and thick, without a tail, with well-developed limbs. The young B. are known by the name of tadpoles , or tetrads, and are formed for an aquatic life; at birth they have a tail, but no feet; gills projecting externally ( Fig . 314, 1), and their skeleton is cartilaginous. But in most B. , these branch iæ soon wither away and disappear, although the aquatic life continues; for the tadpole has internal branch iæ, like fishes, as well as external ( Fig . 314, 2) IMG:content-0556.png:[blocks in formation] these fixed or internal branchise, in the tadpole, are attached under the neck to cartilaginous arches belonging to the hyoid bones, and are protected by the skin; the water reaches them by the cavity of the mouth, and escapes by one or two orifices situated under the neck. In the tadpole of the frog, the hind feet appear first ( Fig . 314, 3), and they become of some length before the fore-feet are visible; these appear later ( Fig . 314, 4). In the salamanders it is the reverse; finally, in the siren, the hind legs never appear. The tail of the tadpole continues to grow in the salamander and proteus, with the rest of the body; but in frogs, and in many others, the tail wastes away and disappears ( Fig . 314, 5 and 6). About the same time the lungs appear, and begin to perform their functions, so that at this period the tadpole is strictly an amphibious animal; but although this strictly amphibious state continues in some, in general it does not; the gills disappear, and in the adult there remain no traces of such an apparatus. In the B. , the lungs are two, equal, and the heart is composed of only one auricle and one ventricle. In the higher forms, the vertebræ are convex at one end, and concave at the other; but in some cases the vertebræ are concave at both ends. The principal families comprised in the cla of B. , are RANIDAE (or frog), HYLOIDE (or tree-toad), SAL AM AND RIDE, and SIRENIDE, q. v. Batra'chi an, n . and a . ( Zool . ) An animal of, or relating to an animal of, the cla Batrachia . Bat'rachoid, a . [Gr. batrachos , a frog, and eidos , shape.) Of frog-like form. Batracholites, ( bai - trai'ko -lites,) n. pl. [Gr. batrachos , a frog, and lithos , stone.] ( Geol .) Fo il remains of frogs and other animals of the same order. The skeletons, vestiges of the soft parts, and imprints of the feet of several genera of true batrachians, occur in the tertiary strata. In the pliocene deposits on the banks of the Rhine at Eningen, and in the paper-coal of the Eifel, several species of frog, toad, and newt have been found. Fo il frogs, of a small species very similar to the recent, abound in a dark shale overlaid by basalt, in the vicinity of Bombay.