Text-Fig. 2. Fig. A, Triakis attenuata n. sp. dermal denticles from high on side at level of 1st dorsal Fig. B, dermal denticle showing underlying base. Figs. C–D, apical and lateral views of dermal denticle Figs. E—F, lateral and dorsal views of portion of dorsal margin of caudal fin showing upper rows of small granular denticles overlying a row of large subcircular denticles, the latter forming a prominence over a semi-naked area which ventrally is bounded by multi-ridged tridentate denticles.

granular subrhomboidal denticles, each with an incipient posterior or posterolateral tooth and numerous low ill-defined ridges Flanking these denticles on each side of the fin, a single row of large subcircular denticles, semi-erect, without distinct denticulation but weakly ridged, and forming a marked prominence along the edge of the fin. Below the row of large denticles an almost naked area, narrow in extent, with well-spaced bluntly tridentate denticles, and below these the normally shaped tridentate denticles.

Head measured to 1st gill-opening 5.8 in total length and less than interspace between 1st and 2nd dorsals. Head greatly depressed with a distinct, thin, flange-like edge, the latter especially prominent from the level of the nostrils to midway between the spiracle and the first gill-opening. Head broad, the least fleshy interorbital distance 3.2 in length of head Snout to eye 2.0 in length of head. Contour of snout tip from above broadly ovate, but just anterior to the eye, the edge of the head extends abruptly to form a distinct step in the contour.

Eye elongate and oval, 3 times as long as high, its horizontal diameter 1.5 in the interorbital. A prominent suborbital fold of skin along anterior two-thirds of eye, well separated from the lower lid anteriorly but continuous with it posteriorly. Spiracle^* ovoid, large, placed slightly below level of centre of eye and behind it by a distance equal to the spiracular length. Longest diameter of spiracle directed posterolateral, its length 3.8 in horizontal diameter of eye. Gill-openings small, the anterior three concave, the 4th and 5th almost straight and above the basis of the pectoral. Length of the gill-openings increasing slightly from the 1st to the 4th the latter being 2.0 in the horizontal diameter of the eye Fifth gill-opening subequal to the length of the 1st. Interspaces between the gills 1.5 to 2.0 in the length of the gill-openings, that between the 4th and 5th the smallest Nostrils oblique, widely separated, the distance between their inner corners 1.7 in the distance from snout to tip of nostril and 4.5 in length of head. The anterior margin of each nostril expanded as a subtriangular lobe directed posteriorly. and the inner portion of the posterior margin developed as a small low folded lobe also directed posteriorly. Mouth broad and highly arched, the apex of the arch acute. Width of mouth 2.2 in length of head, and length of month, measured along midline from anterior of upper jaw to level of the outer angles 4.3 in the same ratio Upper and lower labial furrows equal in length, strongly developed but short, their length 2.5 in the horizontal diameter of the eye.

Teeth 98/114 small, closely crowded so that the successional series overlap. Serial arrangement of teeth primarily anteroposterior, but becoming increasingly oblique towards the angles of the jaws. Both jaws with 5 to 6 series of teeth functional at centre of mouth, 3 to 4 series at the angles. Teeth at angles of mouth considerably different from those at centre, but all comprise essentially a single long pointed erect or slightly oblique major cusp, flanked by one to several mall lesser cusps on each side, borne on a stout base carrying numerous well-defined longitudinal basal striae. The greatest number of lesser cusps produced on those teeth towards the angles of the jaws. In the upper jaw, the 1st to 23rd rows counted from the centre towards the angle of the jaw comprise almost symmetrical teeth with a single long pointed major cusp directed slightly obliquely, flanked on each side by two small pointed lesser cusps, the outermost lesser cusp on each side the smaller; the 24th to 44th rows similar to those medially adjacent but with the large major cusp directed more obliquely, and only on lesser cusp on the lateral side; the 45th to 48th rows with markedly asymmetrical teeth, the major cusp placed well on the lateral side of the tooth, and flanked laterally by one small lesser cusp and medially by three small lesser cusps; tie 49th row similar to those rows just medial but with the major cusp flanked on its lateral side by two small lesser cusps. The teeth in the lower jaw similar to those in the upper jaw, and showing the same general arrangement with the teeth towards the angle of the jaw carrying more medial lesser cusps than those at the centre However this pattern of increase in cusp number is not regular, as some of the paramedian rows carry fewer medial lesser cusps than either the medial or lateral rows. The teeth in the 1st row of the lower jaw are symmetrical with the major cusp flanked by one small lesser cusp on each