Sixteenth Family—Percopsidæ.
Body covered with ctenoid scales; head naked. Margin of the upper jaw formed by the intermaxillaries only; opercular apparatus complete. Barbels none. Gill-openings wide. Adipose fin present.
One genus and species only (Percopsis guttatus); interesting as having the general characters of Salmonoids, but the mouth and scales of a Percoid. Freshwaters of the northern United States.
Seventeenth Family—Haplochitonidæ.
Body naked or scaly (cycloid). Margin of the upper jaw formed by the intermaxillary; opercular apparatus complete. Barbels none. Gill-opening wide; pseudobranchiæ. Air-bladder simple. Adipose fin present. Ovaries laminated; the eggs fall into the cavity of the abdomen, there being no oviduct. Pyloric appendages none.
Fig. 296.—Prototroctes oxyrhynchus, New Zealand.
Freshwater-fishes which represent the Salmonoids in the southern hemisphere. Two genera only are known. Haplochiton (Fig. [104], p. 250) abundant in lakes and the streams falling into the Straits of Magelhæn and in the rivers of Chile and the Falkland Islands. It has the general appearance of a Trout, but is naked. Prototroctes, with the habit of a Coregonus, scaly, and provided with minute teeth; one species (P. maræna) is common in South Australia, the other (P. oxyrhynchus) in New Zealand. The settlers in these colonies call them Grayling; the Maori name of the second species is “Upokororo.”
Eighteenth Family—Gonorhynchidæ.
Head and body entirely covered with spiny scales; mouth with barbels. Margin of the upper jaw formed by the intermaxillary, which, although short, is continued downwards as a thick lip, situated in front of the maxillary. Adipose fin none; the dorsal fin is opposite to the ventrals, and short, like the anal. Stomach simple, without blind sac; pyloric appendages in small number. Pseudobranchiæ; air-bladder absent. Gill-openings narrow.