About Tonna perdix (Linnaeus, 1758)
The common name of this species comes from the shell's brownish color and pattern, which resemble the plumage of a partridge. An adult shell measures between 70 mm and 220 mm in size. The shell is ovate-oblong, ventricose, and rather thin. It has a reddish-brown base color, attractively patterned with white spots arranged in transverse rows; most of these spots are semi-lunar and spaced at varying distances. The spire is conical, slightly projecting, and pointed. It is made up of five to six whorls, which bear numerous ribs that are often widened, weakly convex, and separated by barely noticeable furrows. The suture is very distinct, and is slightly channeled near the body whorl. The aperture is large and subovate, marked with transverse, slightly projecting bands that correspond to the furrows on the shell's outer surface. The inside of the aperture is fawn-colored. The outer lip is thin, everted, and slightly undulated; its entire inner length is decorated with a white band, except for the edge, which is deep brown. The inner lip spreads across the body of the shell. It is very thin and transparent, and ends below in a projecting plate that covers the umbilicus and appears to also form part of it. The columella is smooth and polished, and forms a thick rib to the left of the umbilicus; this rib is marked with transverse striae, and ends at the emargination of the shell's base. The underlying ground color of the shell is bluish white, covered with irregular reddish-brown spots that have a violet tinge. The mollusk's foot shares this color pattern on its underside, while its upper side has furrows formed by wide triangular radiating bands. The tentacles have two brown rings each. This species is found in the Red Sea, the Indian Ocean off Aldabra, Chagos, Madagascar, the Mascarene Basin, Mauritius and Tanzania, and the Pacific Ocean off New Zealand, Australia (Northern Territory, Queensland, Western Australia) and the Galapagos Islands. The mollusk lives in rapid waters and has rather quick movements.
