_a_, Odontoid process; _b_, articular surface for atlas; _c_,
transverse process; _d_; foramen transversarium; _d′_, posterior
opening of _d_; _e_, spine; _f_, posterior articular process.
(Ellenberger-Baum, Anat. d. Hundes.)
]
The =coccygeal vertebræ= are fully developed in the anterior part of the
region. The arch is complete in the first six usually. The first three
or four have well developed articular processes at each end. Behind this
the posterior pair quickly disappears, and the anterior ones become
non-articular and gradually reduced in size. The transverse processes of
the first five or six are relatively large; behind this they quickly
disappear. =Hæmal arches= (or chevron bones) in the form of a =V= or =Y=
occur ventrally at the intercentral junctions of the third, fourth, and
fifth usually. They transmit the middle coccygeal artery, which passes
between pairs of ventral tubercles further back.
[Illustration: