_Rhytina._[119]—No teeth, their place being supplied functionally by the dense, strongly-ridged, horny oral plates. Premaxillary rostrum about as long as the anterior narial aperture, and moderately deflected. Vertebræ: C 7, D 19, L and C 34-37. Head very small in proportion to the body. Tail with two lateral pointed lobes. Pectoral limbs small and truncated. Skin naked and covered with a very thick, hard, rugged, bark-like epidermis. Stomach without cæcal appendages to the pyloric cavity. Cæcum simple. Only one species of this genus is known, _R. stelleri_, the Northern Sea-cow, by far the largest animal of the order, attaining the length of 20 to 25 feet. It was formerly an inhabitant of the shores of two small islands in the North Pacific, Behring and the adjacent Copper Island, on the former of which it was discovered by the ill-fated navigator whose name the island bears, when, with his accomplished companion, the German naturalist Steller, he was wrecked upon it in 1741. Twenty-seven years afterwards (1768), as is commonly supposed, the last of the race was killed,[120] and its very existence would have been unknown to science but for the interesting account of its anatomy and habits left by Steller, and the few more or less imperfect skeletons which have recently rewarded the researches carried on in the frozen soil of the islands around which it dwelt. There is no evidence at present of its having inhabited any other coasts than those of the islands just named, although it can hardly be supposed that its range was always so restricted. When first discovered it was extremely numerous in the shallow bays round Behring Island, finding abundant nutriment in the large laminariæ growing in the sea. Its extirpation is entirely due to the Russian hunters and traders who followed upon the track of the explorers, and, upon Steller’s suggestion, lived upon the flesh of the great Sea-cows. Its restricted distribution, large size, inactive habits, fearlessness of man, and even its affectionate disposition towards its own kind when wounded or in distress, all contributed to accelerate its final extinction. According to Steller’s account, the Rhytina had a skin of a dark brown colour, sometimes spotted or streaked with white. The fore limb was covered with short brush-like hairs. _Extinct_ SIRENIANS.