CRYPTOBRANCHUS, a genus of thoroughly aquatic, but lung-breathing tailed Batrachia, of the family Amphiumidae, characterized by a heavy, flattened build, a very porous tubercular skin, with a frilled fold along each side, short stout limbs with four very short fingers and five very short toes, and minute eyes without lids. The vertebrae are biconcave, and although the gills are lost in the adult, ossified gill-arches, two to four in number, persist. A strong series of vomerine teeth extends across the palate. Three species of this genus are known. One is the well-known fossil of Oeningen first described as Homo diluvii testis and shown by Cuvier to be nearly related to the gigantic salamander of Japan, Cryptobranchus maximus, which has since been found to inhabit China also; the third is the hellbender, mud-puppy or water-dog of North America, C. alleghaniensis, also known under the name of Menopoma. Both the fossil C. scheuchzeri and C. maximus grow to a length of over 5 ft. and are by far the largest Urodeles known, whilst C. alleghaniensis reaches the respectable length of 18 in.
The eggs are laid in rosary-like strings. They have been found, in Japan, deposited in deep holes in the water, where they form large clumps (70 to 80 eggs) round which the female coils herself. The gigantic salamander has also bred in the Amsterdam zoological gardens, the eggs numbering upwards of 500; the male, it is stated, took charge of the eggs, and for the ten weeks which elapsed before the release of the last larva, he kept close to them, at times crawling among the coiled mass of egg-strings or lifting them up, evidently for the purpose of aeration. The larva on leaving the egg is about an inch long, provided with three branched external gills on each side, and showing mere rudiments of the four limbs.