Icelus.—Head large, armed at the gill-covers and on the neck; body with a dorsal series of bony plates from the neck to the base of the caudal; lateral line with osseous tubercles; scattered scales on the sides and abdomen. Ventrals thoracic, with less than five rays. No pectoral filaments. Villiform teeth in the jaws, on the vomer and palatine bones.
Represents Cottus in the far north; I. hamatus is common in Spitzbergen and Greenland, and has been found in abundance in lat. 81° 44’.
Platycephalus.—Head broad, much depressed, more or less armed with spines; body depressed behind the head, sub-cylindrical towards the tail, covered with ctenoid scales. Two dorsal fins; the first spine isolated from the others. Ventrals thoracic, but rather remote from the base of the pectorals. Villiform teeth in the jaws, on the vomer and palatine bones.
Fig. 212.—Platycephalus cirrhonasus, from Port Jackson.
About forty species are known, of which some attain a length of two feet. This genus represents in the tropical Indian Ocean the Cotti of the Arctic, and the Nototheniæ of the Antarctic zone. Like these, they live on the bottom in shallow water, hidden in the sand, the colours of which are assimilated by those of their body. Therefore, they are very scarce near coral islands which are surrounded by great depths; whilst the number of species is rather considerable on many points of the shelving Australian coasts. Their long and strong ventral fins are of great use to them in locomotion. P. insidiator is one of the most common Indian and Australian fishes, and readily recognised by two oblique black bands on the upper and lower caudal lobes.
Fig. 213.—Scale from the lateral line of the same fish.
Hoplichthys, similar to Platycephalus, but with the back and sides of the body covered with bony spiny plates. No separate dorsal spine.
One species, H. langsdorffii, is common on the coast of Japan, and frequently placed dry by the Chinese into their insect-boxes.