ertebrae_ are always eight. In the rock-pigeon all eight
bear ribs; the eighth rib being very thin, and the seventh having no
process. In pouters all the ribs are extremely broad, and, in three out
of four skeletons examined by me, the eighth rib was twice or even
thrice as broad as in the rock-pigeon; and the seventh pair had
distinct processes. In many breeds there are only seven ribs, as in
seven out of eight skeletons of various tumblers, and in several
skeletons of fantails, turbits, and nuns. In all these breeds the
seventh pair was very small, and was destitute of processes, in which
respect it differed from the same rib in the rock-pigeon. In one
tumbler, and in the Bussorah carrier, even the sixth pair had no
process. The hypapophysis of the second dorsal vertebra varies much in
development; being sometimes (as in several, but {166} not all
tumblers) nearly as prominent as that of the third dorsal vertebra; and
the two hypapophyses together tend to form an ossified arch. The
development of the arch, formed by the hypapophyses of the third and
fourth dorsal vertebrae, also varies considerably, as does the size of
the hypapophysis of the fifth vertebra.

The rock-pigeon has twelve _sacral vertebrae_; but these vary in number,
relative size, and distinctness in the different breeds. In pouters,
with their elongated bodies, there are thirteen or even fourteen, and,
as we shall immediately see, an additional number of caudal vertebrae.
In runts and carriers there is generally the proper number, namely
twelve; but in one runt, and in the Bussorah carrier, there were only
eleven. In tumblers there are either eleven, twelve, or thirteen sacral
vertebrae.

The _caudal vertebrae_ are seven in number in the rock-pigeon. In
fantails, which have their tails so largely developed, there are either
eight or nine, and apparently in one case ten, and they are a little
longer than in the rock-pigeon, and their shape varies considerably.
Pouters, also, have eight or nine caudal vertebrae. I have seen eight in
a nun and jacobin. Tumblers, though such small birds, always have the
normal number seven; as have carriers, with one exception, in which
there were only six.

The following table will serve as a summary, and will show the most
remarkable deviations in the number of the vertebrae and rib