along the upper surface of the fin to its tip and parallel to its posterior margin, so as to embrace about one-fifth of the width of the fin. Each denticle of the trunk region with a broad, thin, near horizontal blade. The blades are directed posteriorly, and each is subovoidal in contour but with the posterior margin interrupted by three sharply pointed teeth, a long median tooth, and a short lateral tooth on each side, separated from each other by shallow, incised notches. The external surface of each blade with three major longitudinal ridges, including a median ridge extending the full length of the blade, and one lateral ridge on each side. The median ridge is steep-sided, and sharp-topped distally where it reaches to the tip of the median tooth, but round-topped at the basal end of the blade where it has a shallow, longitudinal groove along its crest. The lateral ridges are lower than the median ridge, broad-topped, and extend to the tip of the lateral teeth, and each is shallowly grooved longitudinally and may carry one and sometimes two minor ridges. The base of each denticle is essentially rhomboidal in outline, with a ridge arising from each of the four major angles on to a strap-shaped pedicle. However, the two anterior margins of the base each have one or two minor angles, which give them a scalloped appearance, and a minor ridge rises on to the pedicle from each of these angles between the major ridges. The denticles on the tail are similar to but smaller than those on the trunk, differing from them only in the lack of scalloping on the anterior margins of the bases, the latter being four-angled and carrying only the four major ridges. The denticles of the interorbital region are of about the same size as those of the trunk, and have the same features except that there are no lateral teeth, and the median tooth is less acutely pointed. The denticles on the margin of the upper lip have smaller, subcircular blades, each with a pointed, median, posterior tooth and lacking lateral teeth. The blades carry the same type of sculpture on their external surfaces as the trunk denticles, but the ridges are wider and heavier with several additional minor ridges on their crests, and are present only at the anterior end of each blade so that the greater portion of the blade is flat-topped and unornamented. The denticles on the lower lip are similar to those on the upper lip except that the blades are thicker and their sculpture extends further along them. At the extreme margin of the lower lip the denticles are squat and almost sessile, and in addition they have a short, thick, median ventral keel beneath the tip of the median tooth but not produced basally.

Head measured to 1st gill-opening 6.8–7.6 in the total length, and about twice the least fleshy interorbital distance. Head slightly depressed, flat above, and broad, with obtusely rounded lateral margins, except anterior to the eyes where there is a distinct dorsolateral edge extending to the tip of the snout. Contour of snout from above bluntly pointed at the snout tip which protrudes as a rounded prominence interrupting the anterior angle, but slightly concave at the level of the nostrils before widening out again anterior to the eyes. Posterior to the eyes the head widens smoothly to reach its maximum width at the level of the gill-openings. Snout short, its length anterior to the eyes just less than the horizontal diameter of the eyes and 2.0–2.2 in the interorbital. Eye large, elongate, and twice as long as high. Spiracle large and sited above and behind the eye so that its lower margin is level with the dorsal margin of the eye and its anterior margin separated from the eye by a distance equal to the spiracular length. Length of the spiracle 2.6–2.8 in the horizontal diameter of the eye. The lateral, anterior and median margins of the spiracle form a smooth, continuous arch, while the posterior margin is straight. Gill-openings small, almost vertical, their anterior margins straight or slightly convex, and forming a horizontal series anterior to and on the same level as the origin of the pectoral fin. Length of the gill-openings decreasing slightly from the 1st to the 5th, the former being 2.0–2.2 in the horizontal diameter of the eye. The interspace between the 1st and 2nd, and 2nd and 3rd gill-openings subequal, and slightly greater than that between the 3rd and 4th, which in turn is greater than that between the 4th and 5th. Nostrils oblique and placed close to the tip of the snout and to the lateral margin, where because of the thickness of the snout they open almost laterally. Distance between the inner corners of the nostrils 1.3–1.4 in the horizontal diameter of the eye. Each nasal aperture subdivided into a circular, anterolateral aperture and an elongate, subovoidal, posteromedial aperture by the posterior nasal flap, which extends anteriorly as a fleshy triangular process from the posterior nasal margin. The anterior nasal margin is produced as a long, low, free flap which almost entirely covers the posteromedial nasal aperture. Mouth broad and little arched. Width of mouth slightly greater than the preoral distance. The upper lip fimbriated and with a narrow, naked margin, the lower lip smooth but with a broad, naked margin. The preoral clefts deeply incised and reaching about half of the distance from the angles of the jaws to the upper symphysis. Posterior to the jaws they are continued by shallowing furrows extending about halfway to the 1st gill-openings.

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Teeth 48/17–18 in the 1,417 mm female, and 23–1–24/17–15 in the 1,197 mm male, dissimilar in the two jaws. The upper teeth each with a single, smooth-edged, sharply-pointed, lanceolate cusp borne on a subtriangular, bifid base, arranged in anteroposterior series, and with several rows functional. Counting from the symphysis, the teeth in the 1st and 2nd series are smaller than those in the 3rd to 10th series, which include the largest teeth in the upper jaw. The

Text-fig. 3.—Scymnodon plunketi, female, 1,417 mm (Dom. Mus. No. 2636). Figs. A-D—Dermal denticles from high on side at level of 1st dorsal. Fig. A—External view of group of denticles. Fig B—External view of one denticle showing underlying base. Fig C—Lateral view. Fig D—Apical view. Fig E—Denticle from interorbital region. Fig F—Denticle from upper lip. Fig. G—Denticle from margin of lower lip. Fig H—Denticle from 0.5 cm behind lower lip. Fig. I—Denticle from caudal fin.

teeth in the 11th to 24th series become increasingly smaller, and instead of having the straight, clongate cusps of the more median teeth, they have short, slightly oblique cusps which are shallowly notched on their lateral margins. In all of the upper teeth, the proximal portion of each cusp which arises from the base, is sculptured with longitudinal ridges, and may be bifid, as is the case in the teeth towards the centre of the jaw. These latter teeth may also have either a rounded prominence or a minute cusp-like structure on each side of the major cusp and just proximal in position to the constriction which gives the cusp its lanceolate form. Three or four rows of upper teeth functional at the centre of the upper jaw, two or three rows towards the angles. The lower teeth each with a single, smooth-edged, sharply-pointed, blade-like cusp borne on a rectangular base, and with one row functional. The bases are higher than broad, and those at the centre of the jaw are narrower than those towards the angles. The cusps are straight-edged, at least for the teeth in the median half of each side of the lower jaw, and recline laterally so that the median margin of each cusp forms the principal cutting edge, and the lateral margin is acutely notched. The teeth towards the angles of the jaws are smaller and have the cusps more oblique than those towards the symphysis so that the most lateral teeth have their median margins almost horizontal. There is no median lower tooth and the first tooth on the left side overlaps the first tooth on the right, while each adjacent tooth overlaps its lateral neighbour.

First dorsal originates by so shallow an angle from the dorsal profile that the actual point of origin cannot be precisely determined. Origin of 1st dorsal spine posterior to the tip of the adpressed pectoral by a distance equal to half the pectoral length. Base of the first dorsal, measured from the origin of the 1st dorsal spine 3.0–3.2 in the length of the head. 1st dorsal brush-shaped and rather elongate, the length of the free posterior margin one-quarter to one-third greater than the length of the base as measured above. Height of 1st dorsal 1.3 in the length of the base. The anterior margin convex, the distal margin straight and the apex smoothly and broadly rounded. The free posterior tip sharply pointed. The 1st dorsal spine short, laterally compressed, and barely interrupting the anterior margin. The 2nd dorsal larger than the 1st, triangular, and with a more acute apex. Origin of the 2nd dorsal above the middle of the pelvic base. Length of the 2nd dorsal base, measured from the origin of the 2nd dorsal spine, 1⅕ that of the 1st dorsal. Height of the 2nd dorsal just less than the length of its free posterior margin, and 1.3 in its base as measured above. The posterior free tip sharply pointed and terminating just anterior to the hypural origin. Caudal