2. The development of bony plates in the skin, found among Mammals only in the Armadillos and their allies. The cast of a section of the tail of a gigantic extinct species (Glyptodon) shows a bony external as well as an internal skeleton.
3. The outer covering modified into true scales, much resembling in structure the nails of the human hand. This occurs in only one family of Mammals, the Pangolins, or Manidæ.
4. Hair in various forms, including bristles and spines. The two kinds of hair composing the external clothing of most Mammals, the long, stiffer outer hair, and the short, soft under-fur, are shown by various examples.
5. The special epidermal appendages found in nearly all Mammals on the ends of the fingers and toes, called according to the various forms they assume, nails, claws, or hoofs.
6. The one or two unpaired horns of the Rhinoceroses, shown by sections to consist of a solid mass of hair-like epidermic fibres.
7. The horns of Oxen, Goats, and Antelopes, each consisting of a hollow conical sheath of horn, covering a permanent projection of the frontal bone (the horn-core).
8. The antlers of Deer, forming solid, bony, and generally branched projections, covered during growth with soft hairy skin, and in most cases shed and renewed annually.
On the wall is arranged a series of antlers of an individual Stag or Red Deer (Cervus elaphus), grown and shed (except the last) in thirteen successive years, showing the changes which took place in their size and form, and the development of the branches, or tines, in each year. In old age the number of these tines tends to diminish.
On the north side of the table-case are shown dissections of the principal internal organs of Mammals.
Bay III. General structure of Birds.