and northward respectively (with some overlap) from the nursery area off KwaZulu-Natal; they join the adults several years later by a yet-unidentified route. In addition, juveniles spend spring and summer in the surf zone and fall and winter in offshore waters, and as they approach in length begin to conduct a north-south migration between KwaZulu-Natal in the winter and the Western Cape in summer. Still-larger sharks, over long, migrate as far as southern Mozambique. Off Western Australia, adult and juvenile dusky sharks migrate towards the coast in summer and fall, though not to the inshore nurseries occupied by newborns. Description One of the largest members of its genus, the dusky shark commonly reaches a length of and a weight of ; the maximum recorded length and weight are and respectively. Females grow larger than males. This shark has a slender, streamlined body with a broadly rounded snout no longer than the width of the mouth. The nostrils are preceded by barely developed flaps of skin. The medium-sized, circular eyes are equipped with nictitating membranes (protective third eyelids). The mouth has very short, subtle furrows at the corners and contains 13-15 (typically 14) tooth rows on either side of both jaws. The upper teeth are distinctively broad, triangular, and slightly oblique with strong, coarse serrations, while the lower teeth are narrower and upright, with finer serrations. The five pairs of gill slits are fairly long. The large pectoral fins measure around one-fifth as long as the body, and have a falcate (sickle-like) shape tapering to a point. The first dorsal fin is of moderate size and somewhat falcate, with a pointed apex and a strongly concave rear margin; its origin lies over the pectoral fin free rear tips. The second dorsal fin is much smaller and is positioned about opposite the anal fin. A low dorsal ridge is present between the dorsal fins. The caudal fin is large and high, with a well-developed lower lobe and a ventral notch near the tip of the upper lobe. The dermal denticles are diamond-shaped and closely set, each bearing five horizontal ridges leading to teeth on the posterior margin. This species is bronzy to bluish gray above and white below, which extends onto the flanks as a faint lighter stripe. The fins, particularly the underside of the pectoral fins and the lower caudal fin lobe) darken towards the tips; this is more obvious in