The full-grown have generally twenty-two or twenty-four teeth in each jaw; and when the mouth is shut, the teeth lock between one another, like the teeth of a trap. The dorsal fin is about fifteen inches high, the tail five feet broad; the pectoral fins are as many, long and comparatively narrow; so that, armed with such excellent paddles, the black dolphin is inferior to none of his relatives in swiftness. Of an eminently social disposition, these dolphins sometimes congregate in herds of many hundreds, under the guidance of several old experienced males, whom the rest follow like a flock of sheep--a property from which the animal is called in Shetland the “ca’ing whale.” No cetacean strands more frequently than the black dolphin, and occasionally large herds have been driven on the shores of Iceland, Norway, and the Orkney, Shetland and Faeroe islands, where their capture is hailed as a godsend. The intelligence that a shoal of ca’ing whales or grinds has been seen approaching the coast, creates great excitement among the otherwise phlegmatic inhabitants of the Faeroe Islands. The whole neighborhood, old and young, is instantly in motion, and soon numerous boats shoot off from shore to intercept the retreat of the dolphins. Slowly and steadily they are driven toward the coast; the phalanx of their enemies draws closer and closer together; terrified by stones and blows, they run ashore, and lie gasping as the flood recedes. Then begins the work of death, amid the loud shouts of the executioners and the furious splashings of the victims. In this manner more than 800 grinds were massacred on August 16, 1776; and during the four summer months that Langbye sojourned on the island in 1817, 623 were driven on shore, and served to pay one-half of the imported corn. But, on the other hand, many years frequently pass without yielding one single black whale to the tender mercies of the islanders. The ferocious orc, or grampus (_Delphinus orca_), is the tiger of the Arctic seas. Black above, white beneath, it is distinguished by its large dorsal fin, which curves backward toward the tail, and rises to the height of two feet or more. Measuring no less than twenty-five feet in length and twelve or thirteen in girth, of a courage equal to its strength, and armed with formidable teeth, thirty in each jaw, the grampus is the dread of the seals, whom it overtakes in spite of their rapid flight; and the whale himself would consider it as his most formidable enemy, were it not for the persecutions of man. The grampus generally ploughs the seas in small troops of four or five, following each other in close single file, and alternately disappearing and rising so as to resemble the undulatory motions of one large serpentiform animal.