The Lower Mammal-Gallery is entered from the western corridor of the central hall. Together with the adjacent corridor, it contains the greater part of the exhibited series of recent Mammals, with the exception of the Cetacea, Sirenia, and Proboscidea, which are downstairs, and the orders Primates, Chiroptera, Insectivora, and Rodentia, which are in the upper gallery. As three special guides[17] are devoted to these galleries, a very brief notice will serve on this occasion. Both stuffed specimens and skulls and skeletons are exhibited, although the former constitute by far the greater portion of the series. A few remains of extinct types, or plaster reproductions of the same, are introduced here and there; and photographs of living animals are hung on the walls, where will also be found some instructive series showing the modifications assumed by the teeth of certain groups. Wherever possible, the horns and antlers of the Ruminants, as well as the horns of the Rhinoceroses, are placed in juxtaposition to the animals to which they respectively belong. [Illustration: FIG. 33.--THE PLATYPUS OR DUCK-BILL (_Ornithorhynchus anatinus_).] [Illustration: FIG. 34.--THE YELLOW-BELLIED PANGOLIN (_Manis tricuspis_) in a characteristic attitude.] [Sidenote: Ruminants, etc.] The series commences on the right side of the gallery with the lowest forms. Down the middle is a row of large Mammals, comprising various Deer, Seals, and Rhinoceroses. On the right of the entrance a small case contains the Australian Platypus or Duck-bill (fig. 33) and the Echidnas of Australia and New Guinea, which lay eggs, and are the lowest of all living Mammals. In the adjacent bay are the Marsupials, such as Kangaroos, Phalangers, or so-called Opossums, Wombats, and Bandicoots of Australasia, and the true Opossums of America. The eighth and ninth bays on the left side contain the so-called Edentate Mammals, such as the South American Sloths, Ant-eaters, and Armadillos, the Scaly Ant-eaters or Pangolins (fig. 34) of tropical Asia and Africa, and the African Aard-Vark or Ant-Bear. The Sea-Cows, as represented by the Dugong, the Manatee, and the recently extinct Rhytina of Bering Island, are shown in the Geological Department. In the second bay are the Pigs and Hippopotamuses; in the third the Camels, and near by the Chevrotains, or Mouse-Deer. Following these are the Deer (_Cervidæ_), many of which, as already stated, are placed in the middle line of the gallery. Properly speaking, the Giraffes and their recent and extinct allies, the former represented by the Okapi of Central Africa (fig. 14, p. 41), should come here; but, as already mentioned, it has been found convenient to remove the Giraffe group into the east corridor of the central hall. In one of the cases in the bays stands the Prongbuck or Pronghorn Antelope (fig. 35), the sole living representative of a family characterised by the circumstance that the horns have hollow branched sheaths which are shed annually.