Sirenians are large mammals resembling seals or whales but they are not closely related to these animals; however strange, the elephant is a closer relative of the sirenians. Sirenians are totally aquatic animals which never come to the ground. Their forelimbs have modified into paddle-like arms used for steering, the tail has modified into a paddle used for propulsion, and the hind limbs are two small, almost invisible remnant bones. Unlike cetaceans, sirenians feed on vegetation. This genus includes three slightly different species, with the American (or West Indian) manatee (Тricherus manatus) being best known of the three. Relative of the American manatee, Steller’s sea cow, once was widely distributed along the shores of Western Aleutian Islands. The last population was discovered by a Russian expedition wrecked on Bering Island in 1741. This population inhabited shallow cold waters around the Commander Islands in the Bering Sea. Steller's sea cow was probably extinct by 1768. The largest animals were 7.5 meters long, and weighed 3.5 tons. Steller's sea cows have a seal-like appearance with a tail which resembled that of a whale or a fish. This animal owes its name to the sea cow females’ milk which was thick and rich in fat, and also to its meat that was similar to beef in taste and texture.