In all the skulls of the large lop-eared rabbits, the supra-orbital plates
or processes of the frontal bones are much broader than in the wild rabbit,
and they generally project more upwards. In the zygomatic arch the
posterior or projecting point of the malar-bone is broader and blunter; and
in the specimen, figure 8, it is so in a remarkable degree. This point
approaches nearer to the auditory meatus than in the wild rabbit, as may be
best seen in figure 8; but this circumstance mainly depends on the changed
direction of the meatus. The inter-parietal bone (see figure 9) differs
much in shape in the several skulls; generally it is more oval, that is
more extended in the line of the longitudinal axis of the skull, than in
the wild rabbit. The posterior margin of "the square raised platform"
(4/25. Waterhouse 'Nat. Hist. Mammalia' volume 2 page 36.) of the occiput,
instead of being truncated, or projecting slightly as in the wild rabbit,
is in most lop-eared rabbits pointed, as in figure 9, C. The paramastoids
relatively to the size of the skull are generally much thicker than in the
wild rabbit.
(FIGURE 10. OCCIPITAL FORAMEN, of natural size, in--A. Wild Rabbit; B.
Large Lop-eared Rabbit.)
The occipital foramen (figure 10) presents some remarkable differences: in
the wild rabbit, the lower edge between the condyles is considerably and
almost angularly hollowed out, and the upper edge is deeply and squarely
notched; hence the longitudinal axis exceeds the transverse axis. In the
skulls of the lop-eared rabbits the transverse axis exceeds the
longitudinal; for in none of these skulls was the lower edge between the
condyles so deeply hollowed out; in five of them there was no upper square
notch, in three there was a trace of the notch, and in two alone it was
well developed. These differences in the shape of the foramen are
remarkable, considering that it gives passage to so important a structure
as the spinal marrow, though apparently the outline of the latter is not
affected by the shape of the passage.
(FIGURE 11. SKULL, of natural size, of Half-lop Rabbit, showing the
different direction of the auditory meatus on the two sides, and the
consequent general distortion of the skull. The left ear of the animal (or
right side of figure) lopped forwards.)
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