An introduction to the study of fishes

by Albert C. L. G. Günther

Fig. 114.—Tooth of Carcharodon rondeletii.

Odontaspis.—The second dorsal and anal are not much smaller than the first dorsal. No pit at the root of the caudal. Side of the tail without keel. Mouth wide. Teeth large, awl-shaped, with one or two small cusps at the base. Gill-openings of moderate width.

Large Sharks from tropical and temperate seas; two species.

Alopecias.—The second dorsal and anal very small. Caudal fin of extraordinary length, with a pit at its root. No keel on the side of the tail. Mouth and gill-openings of moderate width. Teeth equal in both jaws, of moderate size, flat, triangular, not serrated.

This genus consists of one species only, which is known by the name of “Fox-shark” or “Thresher.” It is the most common of the larger kinds of Sharks which occur on the British coasts; and seems to be equally common in other parts of the Atlantic and Mediterranean, as well as on the coasts of California and New Zealand. It attains to a length of fifteen feet, of which the tail takes more than one half; and is quite harmless to man. It follows the shoals of Herrings, Pilchards, and Sprats in their migrations, destroying incredible numbers. When feeding it uses the long tail in splashing the surface of the water, whilst it swims in gradually decreasing circles round a shoal of fishes, which are thus kept crowded together, falling an easy prey to their enemy. Statements that it has been seen to attack Whales and other large Cetaceans, rest upon erroneous observations.

Selache.—The second dorsal and anal very small. A pit at the root of the caudal fin, which is provided with a lower lobe. Side of the tail with a keel. Gill-openings extremely wide. Teeth very small, numerous, conical, without serrature or lateral cusps.

Also this genus consists of one species only, the “Basking Shark” (Pélerin of the French). It is the largest Shark of the North Atlantic, growing to a length of more than thirty feet. It is quite harmless if not attacked; its food consisting of small fishes, and other small marine animals swimming in shoals. On the west coast of Ireland it is chased for the sake of the oil which is extracted from the liver, one fish yielding from a ton to a ton and a-half. Its capture is not unattended with danger, as one blow from the enormously strong tail is sufficient to stave in the sides of a large boat. At certain seasons it is gregarious, and many specimens may be seen in calm weather lying together motionless, with the upper part of the back raised above the surface of the water; a habit from which this Shark has derived its name. The buccal and branchial cavities are of extraordinary width, and, in consequence of the flabby condition of those parts, the head presents a variable and singular appearance in specimens lying dead on the ground. This peculiarity, as well as the circumstance that young specimens have a much longer and more pointed snout than adult ones, has led to the erroneous opinion that several different genera and species of Basking Shark occur in the European seas. The branchial arches of Selache are provided with a very broad fringe of long (five to six inches) and thin gill-rakers, possessing the same microscopical structure as the teeth and dermal productions of Sharks. Similar gill-rakers have been found in a fossil state in the Crag of Anvers in Belgium, proving the existence of this Selachian type in the tertiary epoch. Nothing is known of the reproduction of this fish. The latest contributions to its history are by Steenstrup in “Overs. Dansk. Vidensk. Selsk., Forhandl.” 1873, and by Pavesi in “Annal. Mus. Civ. Geneva,” 1874 and 1878.

Third Family—Rhinodontidæ.

No nictitating membrane. Anal fin present. Two dorsal fins, the first nearly opposite to the ventrals, without spine in front. Mouth and nostril near the extremity of the snout.

This small family comprises one species only, Rhinodon typicus, a gigantic Shark, which is known to exceed a length of fifty feet, but is stated to attain that of seventy. It does not appear to be rare in the western parts of the Indian Ocean, and possibly occurs also in the Pacific. It is one of the most interesting forms, not unlike the Basking Shark of the Northern Seas, having gill-rakers like that species; but very little is known of its structure and mode of life. It is perfectly harmless, its teeth being extremely small and numerous, placed in broad bands; it has been stated to feed on tang, an observation which requires confirmation. The snout is very broad, short, and flat; the eyes are very small. A pit at the root of the caudal fin which has the lower lobe well developed; side of the tail with a keel. A characteristic figure of this fish has been given by A. Smith in his “Illustrations of the Zoology of South Africa,” Plate 26, from a specimen which came ashore at the Cape of Good Hope.