ORDER IV. ABRANCHIA.
(Amphibia without gills.)
North America, which presents us with all the anomalous forms that we have been considering, with the exception of the Proteus, produces two or three species which are still more eel-like in their appearance than the Sirens. The body is greatly lengthened, flexible, and formed for swimming, terminating in a thin, and vertically compressed tail. The skull is solid. There are four limbs, but in one of the genera, these are so widely removed, so short and slender, and so rudimentary, the toes being almost evanescent, as to convey the idea of tentacula rather than feet. But what is most remarkable in these animals, is the peculiarity on which the name of the Order is founded, the absence of branchiæ, or gills. These organs have not been observed at any period of life, but there is an orifice on each side of the neck. Respiration is performed exclusively by lungs, the structure of which is reticulated, and puckered into longitudinal folds: hence these animals are air-breathers, though habitual residents in water. It is believed that this is the permanent condition of their existence, and that they undergo no metamorphosis.
Genus Amphiuma (Gard.).
The very lengthened form, and smooth lubricated skin of these Reptiles renders them exceedingly like eels; a resmblance which is but slightly lessened by the four limbs, as their projection is so small, as but little to modify the general contour of the body; while the toes, which are in one species three and in the other but two on each foot, are minute wart-like divisions without joints or nails. There is an aperture in the neck on each side, whence some have supposed that these animals are possessed of branchiæ at an early stage of their existence; but none have ever been discovered in any specimen. There are teeth in the jaws and in the palate: the former are arranged in a single close-set series along the border of both the upper and lower jaws; the latter are set in two rows running along the margin of the bone called the vomer, and meeting behind at an acute angle. All the teeth are conical, pointed with a slight curve backwards and inwards; their points glisten with a yellow metallic lustre. There are no ribs; the vertebræ present at each extremity a concave surface, thus resembling in structure those of fishes. The eyes are very minute.
The Southern States of North America are the regions which have afforded these singular animals, the intermediate links that unite so imperceptibly the Reptiles with the Fishes. In the stagnant waters of Louisiana, Georgia, South Carolina and Florida, they abound, burying themselves on the approach of winter in the mud at the bottom. In the process of clearing marshy ground, cleansing ponds, &c., immense numbers are sometimes found thus concealed at a depth of three or four feet from the surface. Dr. Harlan was informed by Major Wace, that great numbers in a state of torpidity were thrown up in the winter season, by persons engaged in digging near a street in Pensacola. They were burrowing in the soft mud, two or three feet deep.
TWO-TOED AMPHIUMA.
