About Aplodactylus etheridgii (Ogilby, 1889)
The notchheaded marblefish, Aplodactylus etheridgii, has an elongated body, with body depth roughly equal to one quarter of its standard length. The largest individuals grow a bony ridge above the eye, and the space between the eyes is concave. It has a short snout and a rounded head, with a small slightly downturned mouth, fleshy lips, and a projecting upper lip. Its jaws hold small teeth that are mostly multicuspid, with a smaller number of tricuspid teeth arranged in 3 to 4 rows; the outermost row holds the largest teeth, and there are two patches of vomerine teeth. It has two pairs of nostrils; the front pair has a fleshy flap with cirri on both the front and rear margins. A wide, flattened spine is embedded in the operculum, and does not reach the opercular margin. The dorsal fin has a long base, and is nearly divided in two by a deep, wide incision between its spiny and soft-rayed sections. A notch is visible on the head profile just behind the eye. The dorsal fin contains 15 to 17 spines and 19 to 20 soft rays, while the anal fin has 3 spines and 6 to 7 soft rays. Its large pectoral fins may be longer than the head, and the lowest 5 to 6 rays are unbranched and fleshy. The whole body is covered in small, embedded cycloid scales that extend onto the cheeks and operculum, and form a sheath along the base of the spiny section of the dorsal fin. The maximum recorded total length for this species is 45 cm (18 in). Its body is brown, covered in very small white spots, with large white patches along the flanks, and an orange rear edge to the operculum. It has a grey belly, and brown fins, with the exception of the outer parts of the lower pectoral fin rays, which are yellowish. The notchheaded marblefish is found only around islands in the Tasman Sea, in the southwestern Pacific Ocean. Within Australian waters, it occurs off Lord Howe Island and Norfolk Island. In New Zealand, it can be found at the Kermadec Islands and along the northern coast of New Zealand's North Island. It lives on coastal reefs at depths between 6 metres (20 ft) and 20 metres (66 ft).
