OCR Text |
Show 370 ON A SUPPOSED N E W GALEOCERDO. [May 28, opening exposed; the eye placed over the centre of the small, round, with a round pupil, bronzed silver iris and large granular nictitating membrane. The mouth large, crescentic, near the end of the snout, and with corner folds large above and small below. Body short, thick, keeled on each side from behind the first dorsal to beyond the tail-pits and along the dorsum between the two dorsal fins. The fourth and fifth gill-slits are over the pectoral fin, the last the smallest. The spiracles very small, linear and placed behind the eye, nearly vertical to the corner fold of the mouth. All the fins comparatively small; the first dorsal fin nearly midway between the pectoral and the ventral fins; the second dorsal placed over, but a little in advance of, the anal fin, which last has a deep notch on its posterior border. The upper lobe of the tail is long and curved, having a small lobule terminating in a fine point, with a notch below; lower lobe nearly half as long as the upper one. A large semilunar tail-pit above and below. The colour of the skin is of a slaty hue on the back, marked with transverse bands, interspersed with spots ; the belly white." The following descriptions we make from the series of seven jaws now in the Haslar Museum, and the two Australian jaws preserved by Mr. Rayner with the preparation of dry skin. Teeth, upper jaw-one small central asymmetrical tooth, bending to the left and similar in form to the side teeth, which are considerably larger. In the lower jaw there is one small, central, nearly symmetrical tooth, broad at the base, finely serrate at the sides, giving off, at an acute angle, a denticle on each side, about halfway up, and a central fang which comprises the upper half of the tooth, and which, when seen with a lens, is found to be delicately crenulated. With this exception the teeth are alike in both jaws, and may be described as broad at the base, with a considerable convexity behind, flatter in front, asymmetrical, springing up from the anterior border with a backward curve to form a trenchant fang of a spear-head shape, the posterior border of which only encroaches upon half the width of the tooth; serrate on both sides, the serratures becoming finer towards the summit, while those occupying the hinder half of the tooth are larger and have fine secondary serrations on their edges. About eleven teeth on each side in both jaws, the last three, near the angles of the jaws, diminishing in size. The colour of the dry skin is dingy grey with a certain amount of warmth, which is probably due to exsiccation, and the spots are of a still darker hue. The scales are placed in quincuncial order with wide interspaces, the base of each scale broad, three-rayed and gibbous in front, thus representing the usually rhomboidal base of Shark's scales, the upper part shovel-shaped, somewhat reflexed at the edges, and with an elevated central ridge bifid posteriorly. W e have considered it useful to subjoin a summary of the chief results obtained by a comparison of the two Sharks, G. tigrinus and 67. rayneri, as respectively figured and described by Miiller & Henle and in the present paper. |