III. On the characters of the pelvis in the mammalia, and the conclusions respecting the origin of mammals which may be based on them

In the course of the following observations upon the typical characters and the modifications of the pelvis in the Mammalia, it will be convenient to refer to certain straight lines, which may be drawn through anatomically definable regions of the pelvis, asaxes . Of these I shall term a longitudinal line traversing the centre of the sacral vertebræ, thesacral axis (Plate 8,S. a .); a second, drawn along the ilium, dorso-ventrally, through the middle of the sacral articulation and the centre of the acetabulum, will be termed the iliac axis (II. a .); a third, passing through the junctions of the pubis and ischium above and below the obturator foramen, will be theobturator axis (Ob. a .); while a fourth, traversing the union of the ilium, in front with the pubis, and behind with the ischium, will be theiliopectineal axis (Ip. a.) .