Sirenia, an order of aquatic mammals now represented by the dugong (Halicore) and the manatee (Manatus). Another form, Steller's sea-cow (Rhytina stelleri), was exterminated during the 18th century. In the Miocene and early Pliocene seas there seem to have been abundant Sirenians, many of which belonged to the genus Halitherium. As the characteristics of the dugong, the manatee, and Steller's sea-cow are described in separate articles, it is enough to state here that the Sirenians form a very distinct order, that in spite of their superficial resemblance they have certainly no near affinities with Cetaceans, that at present we must be content to regard them as old-fashioned and, it is to be feared, moribund types, occupying a lowly position in the Mammalian series.
The name, which suggests mermaids, seems to refer to the appearance of the dugong, when it raises its head above the water or carries its young one under its arm.