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89

The skull.

The skull of the Indian Elephant.

90

But the intermaxillaries are in these forms not at all developed
as in the Elephant: the anterior surface of the dental part of the
bone is always rather or quite feebty developed, and the result
of the shortening of the nasal bones is that the bony nasal opening
is extraordinarily large, extending, for instance in the Saiga,
over nearly half the whole extent of the upper surface of the skull
and to a somewhat lesser degree in Alces1 and Gystophora, — while
in the Elephant the bony nasal opening is quite short.

While thus the pars dentalis has in the Elephant become
extraordinarily developed, elongated and posteriorly heightened,
so that the anterior (inferior) border of the bony nasal opening
is, as it were, pushed a considerable distance more backwards than
usual, the processus palatinus has totally vanished; this part of the
intermaxillaries lacks and instead of the two fissnraz palatini there
is only one unpair. This fissure, which is broadest at the anterior
end, extends far back, laterally bordered almost in its whole extent
by the maxillary bones, but having no such anterior boundary as
is ordinarily found in other Mammals. Posteriorly it gets tubular
and ends in the nasal cavity with a long narrow funnelshaped
opening. A somewhat similar considerable extension backwards
of the fissurse palatinse is also found in the Ruminants, where the
organs of Jacobson are lying in the fissures (which are here separated
by the processus palatini of the intermaxillaries) and only
with their posterior end extend above the palatine roof. In the
Elephant the whole organ of Jacobson lies in the fissure and
does not extend into the nasal cavity proper. The canalis Ste-
nonis opens with a minute aperture into the oral cavity, an opening
into the nasal cavity we have not found. The organon Jacob-
soni is very well developed and surrounded by the usual cartilage.

Also in the Tapir the fissurse palatini are united and the
processus palatinus is almost totally lacking (only a small anterior
point is left).

Inferiorly the pars dentalis of the intermaxillary is to a large
extent applied to the maxillary bone, which extends far forwards
below it. To the upper surface of the maxillary, facing the nasal
cavity, is applied a thin flat bone (PI. 32 figs. 5 and 6), the upper
narrower part of which, not being in contact with the maxillary
bone, adjoins the lateral margin of the intermaxillary and borders
the entrance of the maxillary sinus. Medially the said bone borders
the posterior opening of the fissura palatina, posteriorly it
reaches the ethmoideum.

This bone, which we have not found mentioned in the descriptions
of the elephantine skull which we have seen, is evidently
the maxilloturbinal or rather only the basal plate of this bone.
Its place is in reality exactly the same, which the plate-formed
basal part of the maxilloturbinal occupies in other Mammals (PI.
32 fig. 4, PI. 36 fig. 4—7): the inner side of the maxillary from
the intermaxillary unto the ethmoid bone, bordering the entrance
to the maxillary sinus. That it really is this bone is evident from
a direct comparison of a young elephantine skull with skulls of
young Mammals of other groups (we have used longitudinally
intersected skulls of Apes, Dogs and Lambs) on which the turbinate
part of the maxilloturbinal has been cut off so that only
the basal plate is left. If we remember that the foremost part of
the intermaxillary has been extremely raised, the place of the maxilloturbinal
in the Elephant is just that which should be expected.
But the turbinate part has totally disappeared. — The maxilloturbinal
is quite separate in the young Elephant b and perhaps also
in c; but in the older skulls it has to a larger or lesser extent coalesced
with adjoining bones.

The maxilloturbinal backwards borders on the ethmoidal
bone (PI. 32 fig. 5, PI. 31 fig. 5, PI. 30 figs. 3—4); in b it is only
to a limited extent that the two bones meet; in c, in which the
maxilloturbinal plate has a larger extension backwards, the bones
meet in a long line. Otherwise it as usual adjoins to a large extent
the maxillary bone, the surface of both passing smoothly into each
other. Also on the intermaxillary bone the ethmoid borders. In
the skull c it also reaches the nasal bone, in the younger, b, the
two bones are not yet in contact. As usual the ethmoid is on
the sides embraced by the frontals, with which it apparently very

i It may here be noted that in the Ruminants on the whole there is a more or less
pronounced tendency to this same extension of the bony nasal aperture (PI. 34 fig. 1).

early partially coalesces. The ethmoturbinals are rather short;
the uppermost, the nasoturbinale, is very shortened and does not
extend below the nasal bone1. Most of the ethmoturbinals are,
as in several other Mammals (PI. 31 figs. 1—2), placed as it were
in a pocket posteriorly in the nasal cavity. The pocket is above
limited by the lamina cribrosa, below by the lamina transversalis.

The lamina transversalis is the horizontal plate, which represents
the ventral wall of the primary nasal cavity, its anterior margin
being the border of the primary choanal2. It generally appears
as a thin plate, which for instance in the Dog, Phoca a. o.
is of considerable length, while for instance in the Sheep it is
shortened and in the Primates scarcely indicated. The lamina is
formed by the vomer, which is here generally laterally spread
out, by the anterior end of the presphenoid, into which the nasal
cavity is extended, by parts of the ethmoid, and by the palatines.

In the Elephant the lamina transversalis is rather well developed
and is formed of the ethmoid, the presphenoid and the vomer,
the two first named bones forming the bulk of the rather massive
"lamina", which is not as usual a thin plate but of considerable
thickness; to its under side the compressed vomer is appended.

The vomer of the Elephant (PI. 27 figs. 1—4) we have principally
studied in the head of the new-born specimen no. 1 and in the
skulls b, d and g, in which it is still separate, while in many Mammals
(e. g. the Dog, Sheep) it is early coalesced with the ethmoid.
It has the form of a short blade, which has in the new-born Elephant
a height of \—\ of the length; in the three said skulls it
has a height of about \ of the length; in the oldest of the three
specimens the height is relatively the greatest, and in older Elephants
it grows still higher and relatively shorter. The lower
margin of the bone is sharp, the upper somewhat thickened, the
most at its posterior third, where it is applied to the inferior margin
of the presphenoid and of the ethmoid; here also it is rather
deeply longitudinally cleft, while the rest of it has only a shallow
furrow, which is applied to the border of the cartilaginous nasal
septum3. The sides of this cleft are somewhat thickened, and in
the oldest of the three skulls a small air-sinus extends into this
posterior lateral upper part of the vomer from the air-sinuses of
the presphenoid. In still older specimens of the Elephant the said
sinuses of the vomer are somewhat more developed; but the larger
part of the vomer remains non-pneumatic.

In connection with the ethmoid we also must say some words
on the presphenoid (comp. the sagittal sections and PI. 30 figs.
3—4) and its relations to the ethmoid. The presphenoid is rather
shortened; where it meets the basisphenoid, the air-sinuses from
the presphenoid extend into the basisphenoid. The presphenoid
is already in the skull b partially united with the ethmoid. On
some points — dorsally, laterally — the sutures against the ethmoid
are quite distinct, but on other points — ventrally — they are
scarcely discernible or quite obliterated. While the upper part of
the lamina cribrosa is not yet ossified in this young skull, the
lamina perpendicularis of the ethmoid is already fused with the
presphenoid, only a feeble indication of its having been separate
from this is to be found on the inner side of the cranial cavity
in the form of an obliterated suture.

The bony outer nasal opening having by the Elephant been drawn
backwards, the nasal bones are extraordinarily shortened, their
length being, apart from the anterior tip, minor than the breadth.
They have as it were also drawn the intermaxillaries backwards
and jointly with the upper hind ends of these they have taken
place in a deep bay in the anterior margin of the frontals; the
bay extends even in young Elephants somewhat behind the proc.
postorbitalis, while the anterior margin of the nasal bones in such
young specimens (d, PI. 22 fig. 3) is placed off the same process.
On the contrary the maxillary bones have not kept pace but stop
at the anterior margin of the orbita, do not at all reach the nasal
bones and only on a limited point the frontals.

1 As to more details respecting the ethmoturbinals comp. the decription of the nasal
cavity.

2 Comp. Boas, Schlafenuberdachung etc. in: Morph. Jahrb. 49. Bd., p. 304.

3 In the skull b2 the vomer is furnished with the lateral wings which are present
in many Mammals and apply themselves to the palatinum and maxillary. In this specimen
they are very well developed as thin plates extending over parts of the two named
bones. In the other specimens — also in b — they are but slightly indicated (in some
specimens at our disposal, for instance b\, the vomer has accidentally been lost, so that
it has been impossible to ascertain the shape of the vomer in them).