The most important of the whaleboned whales is the Greenland, or Arctic Right, whale. It attains a length of upwards of 45 to 50 ft., and is remarkable for the enormous extent of its head and mouth cavity. The head extends for a third of the length of the body, so that the mouth cavity may be as much as 18 ft. long, 12 ft. broad and 11 ft. in height, the dimensions of a small chapel! The upper jaw is narrower than the lower and arches backwards, thus increasing the actual height of the mouth cavity and providing ample room for the blades of whalebone with which the jaws are furnished in place of teeth. These blades of whalebone number about 380, and range in length from 8 ft. to, in exceptional cases, 12 ft. They are suspended in the mouth of the whale like stalactites, set fairly close together, and, since the edges of each blade are fringed with fine whalebone, the whole arrangement forms a very efficient strainer. This enables the whale to feed upon the plankton—or “krill,” as it is called by the whalers—and small fish, e.g. herring and capelan. The whale fills his enormous cavern of a mouth with water containing the floating food particles, and then, by raising his tongue, slowly expels the water through the whalebone sieve. The food particles are retained by the whalebone, and are then licked off and swallowed. The Greenland whale inhabits the Arctic seas north of latitude 54°N. A closely related variety, the Bowhead whale, forms the basis of a fishery in the Behring Sea. The largest whales known are the so-called Rorqual whales. The name of these whales is derived from the large number of longitudinal folds or pleatings that form a characteristic feature of their throat. Rorqual whales attain a length of from 80 to 85 ft. The head is relatively small, and the long, slender body carries a distinct dorsal fin. The whalebone is coarse and short. The Rorqual whales are the most abundant and widely distributed of all whales. They are found in all open seas, with the exception of those in the extreme Arctic and Antarctic regions. The Southern Right whale, or Black whale, is found in the temperate seas of both Northern and Southern hemispheres. [Illustration: FIG. 20 A WHALE’S MOUTH The carcass is ready for cutting up at a Shetland whaling station.] Of the toothed whales, the most important is the Cachalot or Sperm whale. It is chiefly captured in Southern seas, and is killed in large numbers for the sake of the spermaceti and sperm oil that occur in large quantities in its head cavity. Sperm and other toothed whales feed upon fish and cuttlefish.