Art. XX.—On Cheimarrichthys fosteri, a New Genus belonging to the New Zealand Freshwater Fishes.
[Read before the Philosophical Institute of Canterbury, 4th December, 1873.]
Amongst a collection of fishes, consisting principally of specimens of Galaxias brevipinnis and Retropinna richardsonii, obtained by Mrs. J. C. Foster, of Sumner, during the month of March, in the Otira, where that alpine torrent leaves its picturesque gorge, I observed a few specimens, four to five inches long, which were unknown to me, and on examination were found to be new to science. They proved to belong to a genus hitherto undescribed, forming part of the Trachinina, the second group of the TrachidŒ, of which, as far as I am aware, only another genus (Aphrites) is a freshwater fish inhabiting the rivers of South America and Tasmania, but from which the species under consideration differs materially.
Body stout; head spatuliform, broad and depressed, scaleless; opening of mouth slightly oblique, and with the upper jaw longer; eyes lateral, somewhat directed upwards; scales small ctenoid; villiform teeth in both jaws, and on the vomer.
Two separate dorsals, the first consisting of three small but strong and sharp spines, of which the third is the largest; each with a small posterior membrane, so as to prevent the spine from rising to the vertical. Ventrals jugular; pectoral rays branched. Opening of gills large.
Operculum and præoperculum entire; six branchiostegals; lateral line continuous.
D. 3 | 19; V. 1 | 6; P. 11; A. 14.
The length of the head is one fifth of the total length (without caudal fin), which is equal to the greatest height of the body.
Eyes near the upper side of the head; diameter of eye one fourth of the head; interorbital space convex, scarcely more than the diameter of the eye. Of the soft but strong dorsal spines, the second is the longest, after which they gradually diminish; of the anal, the spines rise to the third, which is the longest, both fins being similarly developed. The anal fin begins below the fifth ray of the dorsal, and extends a little further than the former.
Scales behind the head to the beginning of the soft dorsal, and above the lateral line, very small.
Colour of head dark olive green, cheeks paler; upper portion of body above
lateral line of the same dark green shade, but as we advance from the head towards the caudal fin becoming gradually lighter; now and then vertical and somewhat indistinct bands of a darker shade extending across the lateral line; of them the last, at the base of the caudal fin, is the darkest and most conspicuous. Below lateral line pale olive green. Chin and belly white. Pectoral, caudal, and ventral fins mottled dark olive green, with a somewhat linear arrangement; dorsal and anal fins mottled dark olive green in their upper portion only.