The largest of marine fishes, _Rhinodon_, _Selache_, _Carcharodon_, _Myliobatidæ_, _Thynnus_, _Xiphiidæ_, _Orthagoriscus_, belong to the Pelagic Fauna. Young fishes are frequently found in mid-ocean, which are the offspring of shore-fishes normally depositing their spawn near the coast. The manner, in which this fry passes into the open sea, is unknown; for it has not yet been ascertained whether it is carried by currents from the place where it was deposited originally, or whether shore-fishes sometimes spawn at a distance from the coast. We may remember that shore-fishes inhabit not only coasts but also submerged banks with some depth of water above, and that, by the action of the water, spawn deposited on these latter localities is very liable to be dispersed over wide areas of the ocean. Embryoes of at least some shore-fishes hatched under abnormal conditions seem to have an abnormal growth up to a certain period of their life, when they perish. The _Leptocephali_ must be regarded as such abnormally developed fish (see p. 179). Fishes of a similar condition are the so-called Pelagic _Plagusiæ_, young Pleuronectoids, the origin of which is still unknown. As mentioned before, Flat-fishes, like all the other Anacanths, are otherwise not represented in the Pelagic fauna. [Illustration: Figs. 109 and 110.--_Antennarius candimaculatus_, a pelagic fish, from the Indian Ocean.] CHAPTER XXI. THE FISHES OF THE DEEP SEA. The knowledge of the existence of deep-sea fishes is one of the recent discoveries of ichthyology. It is only about twenty years ago that, from the evidence afforded by the anatomical structure of a few singular fishes obtained in the North Atlantic, an opinion was expressed that these fishes inhabited great depths of the ocean, and that their organisation was specially adapted for living under the physical abyssal conditions. These fishes agreed in the character of their connective tissue, which was so extremely weak as to yield to, and to break under, the slightest pressure, so that the greatest difficulty is experienced to preserve their body in its continuity. Another singular circumstance was, that some of the specimens were picked up floating on the surface of the water, having met their deaths whilst engaged in swallowing or digesting another fish not much inferior or even superior in size to themselves.