Triakis attenuata n.sp. from New Zealand waters has the second dorsal originating just anterior to the anal origin and the rear tip extending beyond the rear tip of the anal; the first dorsal originating above the pectoral insertion with the rear tip terminating well anterior to the pelvic origin.

The genus Triakis includes those smooth dogfishes in which the nostrils are distinct from the mouth; the anterior margin of the nostril is expanded as a small lobe but not produced as a nasal barbel; the teeth are small, crowded and carry a pointed major cusp flanked by one to several lesser cusps on each side; a labial furrow is present on each jaw; and the spiracles are relatively large. Species of this genus are known from the western North Pacific, the China Sea, the eastern Pacific both north and south, and Cuban waters in the Atlantic. Bigelow and Schroeder (1948) also give Indian Ocean (including the Red and Arabian Seas), Malaysia, Melanesia and Polynesia, but in a private communication Schroeder says that these localities are included due to an error in transcription. One species, T. scyllia Muller and Henle 1841, known from Japan, Korea, China and Formosa, has once been recorded from South Australia, but Whitley (1940, p. 115) doubts the validity of this record. There appears to be no record of the genus from New Zealand waters.

In December, 1953, the S.T. “Maimai” was trawling off the southern part of the East Coast of the North Island, in much deeper water than usual, due to a local scarcity of fish on the shallower (40 to 50 fathoms) grounds, and collected from 120 fathoms one specimen of smooth dogfish which was very unlike the smooth hound Mustelus lenticulatus Phillipps 1932, normally taken in the trawl. This specimen was very attenuate, almost anguilliform as though emaciated, but with a flat depressed head. It was complete, but showed recent injuries in the form of two vertical rows of tooth punctures, traversing the whole depth of the right side of the body at the level of the 1st dorsal, with some of them at least perforating the abdominal wall. The specimen was recognised as a novelty, kept in cold storage, and later given to the author. This specimen forms the basis for the following account of a new species of Triakis.

Bigelow and Schroeder (1948) recognise seven species of Triakis. Using the position of the 2nd dorsal relative to the anal, and the length of the labial furrows as key characters, they group T. venusta and T. barbouri in having the 2nd dorsal orig n. over or behind the origin of the anal with its rear tip over or posterior to the tip of the latter, and short labial furrows. The remaining species, T. maculata, T leucoperiptera, T henler, T. scyllia and T. semifasciata have the 2nd dorsal

approaching the condition seen in the genus Mustelus where the teeth are without distinct cusps but have a sinuous edge. T. venusta has teeth which are intermediate in character, bearing moderately long major cusps. With regard to teeth number in those species with long major cusps, T. barbouri has 62 to 62/60 to 62 (Bigelow and Schroeder, p. 239); T. scyllia 40/36 (Fowler, p. 198), and T. leucoperiptera 18/34 (Fowler, p. 197). I have no information on T. semifasciata. The “Maimai” specimen has 98/114, and is thus clearly separable from the species listed above. The presence of a high tooth number in the “Maimai” specimen and T, barbouri suggests a closer relationship between these two species than between them and any of the other species, a postulate borne out by the similarities in denticle and tooth structure, relative fin positions, etc., mentioned above. The dental formula 18/34 for T. leucoperiptera quoted from Fowler (1941, p. 197) appears to be at variance with that occurring in the majority of sharks, where tie difference between the number of teeth in the upper and lower jaws is not more than a few per cent. If the formula is correct, then considerable weight needs to be placed on the further statement in Fowler's description ‘the remaining rows of teeth (towards angle of lower jaw) smaller than opposing upper teeth.’

The number and site of the lesser cusps on the teeth vary extensively in the different species, and hence offer data for comparison. Both species with short major cusps, T. maculata and T. henlei, have one lesser cusp on each side of the major cusp, though frequently the medial lesser cusp is missing. The remaining species, and the “Maimai” specimen, have one to several lesser cusps on each side, the teeth at the centre of the mouth usually with fewer lesser cusps than those towards the angles. These latter species may be divided into three groups, depending on whether the number of lesser cusps is uniform on each flank of the major cusp or whether more lesser cusps are present on either the medial or lateral flank. I have been unable to locate full descriptions of the dentition of T. venusta, T. scyllia and T. semifasciata, but the meagre information available suggests that these spacies have symmetrical teeth with from one to three lesser cusps on each side of the major cusp, the number depending on the position of the tooth in the jaw. T. leucoperiptera appears to be alone in having the greater number of lesser cusps on the lateral flank of the major cusp—the teeth towards the angles of the lower jaw bearing up to four lateral lesser cusps and no medial ones (Fowler, p. 197). T. barbouri and the “Maimai” specimen agree in having a majority of lesser cusps on the medial flank; but in the former species up to three medial cusps may be present and no lateral cusp, while in the “Maimai” specimen there may be as many as five medial cusps and at least one lateral cusp is always present.

There does not appear to be any correlation between the groupings of the species with regard to colouration, including maculation, and those arrived at using the already described morphological characters. The “Maimai” specimen is plain coloured, as are T. leucoperiptera and T. henlei The remaining species are obviously patterned, with the exception of T. barbouri, which is generally plain but shows faint maculation in some specimens.

On the basis of the distinctive attenuation of the “Maimai” specimen, and the other afore-mentioned morphological differences between it and the known species of Triakis, I propose it as the type of a new species, T. attenuata.