4. =Unfeathered= (_Implumis_). A portion of skin in which no feathers
are inserted.
5. =Upper parts= (_Notæum_). The entire upper surface of the animal.
(Sometimes restricted to the trunk.)
6. =Lower parts= (_Gastræum_). The entire lower surface of the animal.
(Sometimes restricted to the trunk.)
7. =Anterior portion= (_Stethiæum_). The forward part of the body
(about half), both upper and under surfaces, including the chest.
8. =Posterior portion= (_Uræum_). The hinder portion of the body
(about half), including the abdominal cavity.
B. The Head (_Caput_).
9. =Bill= (_Rostrum_). The projecting jaws, one above the other,
united by a hinge joint behind, and covered by a horny sheath, or a
skin, and enclosing the mouth.