=The Snake-head Mullets: Ophicephalidæ.=—The family of _Ophicephalidæ_, snake-head mullets, or China-fishes, placed among the _Percesoces_ by Cope and Boulenger, seems to us nearer the Labyrinthine fishes, of which it is perhaps a degenerate descendant. The body is long, cylindrical, covered with firm scales which on the head are often larger and shield-like. The mouth is large, the head pike-like, and the habit carnivorous and voracious. There are no spines in any of the fins, but the thoracic position of the ventrals indicates affinity with perch-like forms and the absence of ventral spines seems rather a feature of degradation, the more so as in one genus (_Channa_) the ventrals are wanting altogether. The numerous species are found in the rivers of southern China and India, crossing to Formosa and to Africa. They are extremely tenacious of life, and are carried alive by the Chinese to San Francisco and to Hawaii, where they are now naturalized, being known as "China-fishes." [Illustration: FIG. 304.—_Channa formosana_ Jordan & Evermann. Streams of Formosa. ] [Illustration: FIG. 305.—Snake-headed China-fish, _Ophicephalus barca_. India. (After Day.) ] These fishes have no special organ for holding water on the gills, but the gill space may be partly closed by a membrane. According to Dr. Günther, these fishes are "able to survive drought living in semi-fluid mud or lying in a torpid state below the hard-baked crusts of the bottom of a tank from which every drop of water has disappeared. Respiration is probably entirely suspended during the state of torpidity, but whilst the mud is still soft enough to allow them to come to the surface, they rise at intervals to take in a quantity of air, by means of which their blood is oxygenized. This habit has been observed in some species to continue also to the period of the year in which the fish lives in normal water, and individuals which are kept in a basin and prevented from coming to the surface and renewing the air for respiratory purposes are suffocated. The particular manner in which the accessory branchial cavity participates in respiratory functions is not known. It is a simple cavity, without an accessory branchial organ, the opening of which is partly closed by a fold of the mucous membrane." _Ophicephalus striatus_ is the most widely diffused species in China, India, and the Philippines, living in grassy swamps and biting at any bait from a live frog to an artificial salmon-fly. It has been introduced into Hawaii. _Ophicephalus marulius_ is another very common species, as is also _Channa orientalis_, known by the absence of ventral fins.