I havb never seen the skeleton of Ptiloeercns, which Mivart refers to the family
Tupaiidw along with JELylomys ; but as an inspection of the skeleton of the latter has
not verified his presumption that it agreed with Tupaia in having its tibia
and fibula distinct* it is impossible to say what characters Ptilocereus may present
in that respect..
The vertebral column of Tvpaia has an upward curve in the cervical portion,
and the dorso-lumbar region is curved convexly-—-an arrangement of the vertebrae
which would lead to the conclusion that the animal was in the habit of sitting
with its body raised as the squirrels do, and which I have observed to be the
case. The leading features which first present themselves are: the moderately
broad, thin, spinous plate of the axis, which appears large owing to its close
apposition to the narrow and rather short spinous processes of the cervical and
dorsal vertebrae; the depressed, overlapping spinous process of the three dorsal
vertebrae bearing free ribs* and of the lumbar with their well-developed transverse
processes; the rapid enlargement of the vertebrae in the lumbar region;
the rather small sacrum, consisting of three vertebrae; and, lastly, the long and
tapering tail.
There are 18 dorsal and 6 lumbar vertebrae with 23 caudal vertebrae or more.
The spinous process, if we except the axis, is fully developed in the cervical
region. I t first becomes distinctly visible in the 5th vertebra, increasing in size
to the 7th. The spinous process of the 1st dorsal is nearly erect, whilst the
2nd is slightly stronger and broader antero-posteriorly, but about the same length
and directed slightly backwards. The 3rd is still stronger and a little more
lengthened and backward in its direction, while the 4th is almost its fellow. The
5th is not so broad from before backwards as the 4th, which it exceeds in length;
and the 6th shows a distinctly more marked backward inclination and is also
narrower than the process on either side of it. The 7th, 8th, and 9th processes
increase gradually in antero-posterior expansion, but dimmish in length, the 9th
being almost triangular, with a broad base. The 10th process is smaller than the
9th, with a sharp triangular point with its apex directed forwards. The 11th is
quite distinct from those preceding it, and has its apex extended from before backwards,
and directed forwards over the lower two-thirds of the hinder margin of the
10th process. I t is short and rather broad antero-posteriorly. The 12th and 13th
spinous processes are low and broad from before backwards, and overlap the vertebrae
in front of them. . The first lumbar process resembles the last mentioned, but
the one succeeding it is not so depressed, and is every way larger. As the processes
are traced backwards to the last lumbar vertebrae they become larger and more erect,
although still directed forwards. The spinous process of the 1st sacral is low
and ridge-like, but in the 2nd vertebra it is moderately large and bent slightly
forwards. In the 3rd sacral it is lower than in the last and slopes faintly backwards,
and the process, although moderately developed in the 1 st caudal, rapidly diminishes
in size and disappears in the 3rd, being continued to the 6th as an obscure ridge
which is lost in the 7th segment.
The transverse •process is most strongly developed in the 5th lumbar vertebra
where it has the most antero-posterior extension, as a thin, almost transparent plate
of bone directed much forwards. The process is very small in the 1st lumbar
vertebra, and in the last dorsal it is reduced to an obscure ridge above the articulation
of the rib and disappears in the 12th dorsal. I t again shows itself in the 11th
dorsal, projecting as an obscure ridge over the head of the rib. I t increases in size
to the 9th vertebra, after which it maintains a nearly uniform size to the 6th dorsal
segment, anterior to which it is more extended outwards, attaining its matimum
extension in the 7th cervical. The pleuropophysial plate of the 6th cervical vertebra
is contracted from before backwards at its base, its free extremity being considerably
extended in that direction. The pleuropophysial processes occur in the
5th and 4th vertebrae, and are directed forwards and inwards, and they can be traced
as a ridge in the 3rd vertebra. The transverse processes of the 1st and 2nd caudal
vertebrae are at right angles to the centrum and do not project beyond the lateral line
of the sacrum. They have a moderate antero-posterior extension and are slightly
dilated at their extremities. The processes of the 3rd and 4th .caudals are curved
backwards, convex anteriorly and concave posteriorly. The 5th of either side
forms an almost quadrangular figure, but with concave sides and slightly concave
posteriorly. In the succeeding vertebra the concavity of the sides is so great
as to reach the centrum, so that only the anterior and posterior .extremities of
.the process remain at either extremity of the vertebra, one directed forwards and
the other backwards, becoming very obscure as they are traced Wards the extremity
of the tail.
In the lumlbar region the metapophyses only become to be distinguished and
separate from the zygapophyses about the 1 st or 2nd vertebra, and anterior to that
they become stronger; but gradually, from the more ventral disposition of the
zygapophyses which they follow, they come in contact with the transverse process
at the 10th vertebra, and in the 9th are in close connection with it. They can be
traced as far forwards as the 4th dorsal vertebra. The zygapophysis of the 1st sacral
vertebra is well developed, and it is succeeded by two small processes on a line with
it, one behind the other, suggesting that they are more of the nature of rudimentary
zygapophyses than metapophyses. In the tail the metapophyses reach
their greatest development while in connection with the zygapophysis at the 4th
caudal vertebra, and as beyond that segment there are no posterior zygapophysial
facets, the metapophysis becomes well marked in a few vertebra*, but rapidly dwindles
away as we trace it backwards.
The anapophyses first show themselves in the 4th lumbar vertebra as small,
almost styliform processes, increasing in size to the 12th dorsal, before which they
decrease in size, and are brought into close contact with the metapophyses, but they
•can be detected as far forwards as the fourth dorsal.
Hyperapophyses begin to show in the 1 1 th dorsal, increasing in size to the 4th
lumbar, decreasing in size to the 5th, and entirely absent in the 6th. In the 3rd
cervical vertebra of T. belongeri there is a small process corresponding in position to