Vestiges of gills appear also on the hyoid and on the mandibular arch, but on the latter they are of very short duration. Those of the hyoid gradually fuse with the first of the branchial gills, and these also concentrate with their bases so that they ultimately seem to spring from one common stem. Brauer remarks that the distinction between internal and external gills seems to be one of degree only; the hyoidean and mandibular gills namely start from the hinder margin of the arches, just like the internal gills of _Torpedo_ according to Ziegler, while the other gills start from the sides of the branchial arches. He also found a pair of little swellings behind the last gill-cleft, and an unpaired swelling (corresponding with a double one in _Ichthyophis_) in front of the vent. Not unreasonably he sees in these swellings the last, very transitional vestiges of the paired limbs. _Typhlonectes compressicauda_ of Guiana and Venezuela is one of the largest Coecilians, reaching a length of 18 inches, with a body-diameter of ¾ inch. The general colour, as in most of these creatures, is olive brown to black. A sort of adhesive disc surrounding the vent occurs in this genus. Peters, who described this species, found in one female six embryos of comparatively enormous size, one of them being 157 mm. (more than 6 inches) long, and 12 mm. thick, and devoid of a tail-fin. Instead of lateral gill-openings there is a "bag" on each side 55 mm. long, upon which is distributed a blood-vessel. The Sarasins have examined the same specimen: The gills are not a bag, but consist of two flat, unbroken membranes which are closely connected with each other. In fact the outer gills of all Amphibia may be said to begin in the shape of small bags, whence sprout secondarily the gill-fringes; but in _Typhlonectes_ they form these flaps instead of growing into the usual three gills. The embryos have no epidermal sense-organs, but plenty of skin-glands. Probably when born they take at once to terrestrial life, the flaps are possibly shed at birth, and there remains a little cicatrix. _Dermophis thomensis_ of West Africa (its other relations live in East Africa, South and Central America) is also viviparous. {94}CHAPTER V LISSAMPHIBIA (_CONTINUED_)–URODELA ORDER II. URODELA OR TAILED AMPHIBIA. The recent tailed Amphibia, Salamanders and Newts in the wider sense, have been grouped into four families which can be conveniently diagnosed by the following characters:– Both the upper and lower jaws are furnished with teeth. Fore- and hind-limbs are always present. Maxillary bones present. Eyes free and devoid of lids .......... AMPHIUMIDAE, p. 97. Eyes with movable lids[45] .......... SALAMANDRIDAE, p. 102. Maxillary bones absent. Eyes without lids. Perennibranchiate .......... PROTEIDAE, p. 132. Both jaws are toothless. The hind-limbs, the maxillary bones and eyelids are absent. Perennibranchiate .......... SIRENIDAE, p. 136.