Of the only two Elasmobranchs, one, namely _Raia hyperborea_, has been found in water extending from 400 to 608 fathoms in depth. Only four specimens have yet been taken, one by the Norwegian expedition off Spitzbergen and three by the ‘Knight Errant’ off the northern coasts of Scotland. It is interesting to find that this, the only deep-sea species of the Rays, shows some striking peculiarities. ‘The teeth are remarkably slender,’ says Günther, ‘small, irregularly and widely set, different from those of other British Rays. In young specimens at any rate those of the male do not differ from those of the female. The mucous membrane behind the upper jaw forms a pad with a lobulated surface. The mucous cavities of the head are extremely wide, and finally the accessory copulatory organs have a spongy appearance, and are flexible, the cartilage by which they are supported being a simple slender rod.’ The other Elasmobranch, that extends into very deep water, is _Chimæra affinis_, a species which can hardly be distinguished from the better known _Chimæra monstrosa_, a fish that itself very frequently wanders within the limits of the abysmal zone. Among the Teleostei, the family Berycidæ has several representatives in the deep water. They are small fish rarely exceeding four inches in length, with large heavy heads, with functional but small eyes, and an abundant supply of large mucous glands on the skin. _Melamphaes beanii_, belonging to this family, has been captured at the enormous depth of 2,949 fathoms. _Bathydraco antarcticus_, belonging to the family Trachinidæ, from a depth of 1,260 fathoms, is an example of a true abysmal fish possessing very large eyes. The Pediculati, the family of the anglers, is represented at depths of over 2,000 fathoms by the interesting form _Melanocetus Murrayi_. The eyes are very small indeed, the mouth huge and armed with long uneven rasp-like teeth. At the end of the fishing-rod tentacle hanging over the mouth, there is an organ that has been supposed to be capable of emitting a phosphorescent light. This curious modification of the red worm-like bait of the common shallow-water angler into a will-o-the-wisp lantern attracting little fishes to their destruction in the deadly jaws of the _Melanocetus_ is one of the most interesting adaptations that have been brought to light by our study of the deep-sea fauna. Several species of the family Lycodidæ occur in the abysmal zone, but they do not possess any features that call for special mention in this place. [Illustration: FIG. 21.—_Melanocetus Murrayi_, 1,850–2,450 fathoms. (After Günther.)] The family Ophidiidæ contributes very largely to the fish fauna of the abyss. Some of the deep-water genera, such as _Neobythites_, have a wide bathymetrical distribution extending from 100 fathoms to depths of over 2,000 fathoms, but others, such as _Bathyonus_, _Typhonus_, and _Aphyonus_, only occur in depths of over 1,000 fathoms.