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The ethmoid and the pneumatic sinuses.

The ethmoid.

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nasal cavity, its olfactory fold being shortened (measured in rostro-
caudal direction) and formed as a simple rolling of the rostral margin
; only in the most rostrally prominent, rounded part there is an
indication of this elongation.

The ethmoid contains 7 endoturbinals and 32 ectoturbinals1
which are distributed and specifically arranged as seen on PI. 45
fig. 2. The ectoturbinals are arranged in several rows. For the
purpose of comparison with the two other examined crania, two
ectoturbinals in Chang are marked 27 a and 28 a. In the left half
of Chang's head the 15th ectoturbinal sends a short narrow elongation
in between the olfactory folds of the first and second endoturbinals
, where it is distinctly visible, whilst the other part of
the ectoturbinal is concealed by the two olfactory folds. That the
number of olfactory folds in the row of endoturbinals can thus
be increased by an ectoturbinal has also been observed in a few
cases in Bos.

The basal lamellae of the turbinals are remarkable for their
very considerable breadth, decreasing on the ventral turbinals as
in the ethmoid of other Mammals. Several basal lamellae are besides
also rather thick, although but rarely in the whole of their
length and breadth. Where they take their origin from the lamina
cribrosa and the lamina lateralis they are thin, but increase in
thickness towards the rostral end, though not always smoothly.
At the origin of a secondary leaf a basal lamella may be very
much thickened. The greatest thickness was stated on the basal
lamella of the fourth endoturbinal, measuring 3 mm where it is
the thickest, the basal lamella of the 6. endoturbinal measuring
up to 2 mm. The bony tissue of them was compact and uncommonly
firm and hard. Finally the turbinals are characterized

by being supplied with numerous secondary rolled-up lamellae.
In several turbinals we meet with the feature also known from
other Mammals that a secondary lamella splits from the basal
lamella at a shorter or longer distance from the lamina cribrosa,
and continues ventrally to the lamina lateralis as an apparently
independant turbinal; the 25. lamella (textfigure) issues from the
3. endoturbinal, the 26. from the 27. ectoturbinal, the 29. and the
30. from the 4. endoturbinal; the 14. ectoturbinal and the 2. endoturbinal
are split close below the lamina cribrosa each into two
lamellae which again unite ventrally. At the 15. ectoturbinal we
meet with the peculiarity that the 16. and the 18. ectoturbinals,
which issue independently from the lamina cribrosa, unite with
the 15. ectoturbinal while proceeding further ventrally. The 19.
ectoturbinal emits a second lamella to the 15. Finally it ought
to be mentioned that the olfactory folds on the endoturbinals may
be secondarily folded; this is the case with the 2. and the 3., to
a lesser degree with the 7.

In the Elephants c and h (PI. 45 figs. 1 and 3) the ethmoid
also holds 7 endoturbinals, mainly of the same structure as those
in Chang; the olfactory folds in the young c are, however, not
yet fully developed. There are 30 ectoturbinals, as there are only
2 between the 4. and 5. endoturbinals; in Chang, on the contrary,
there are 4, of which the two marked 27 a and 28 a in PI. 45 fig. 2
are possibly secondary leaves which have been split off, or they may
be due to the fact, well known in other Mammals, f. inst. Canis,
that the number of ectoturbinals is not constant, not even in the
same species. The arrangement of the rows of ectoturbinals is
also differing somewhat from that in Chang, a fact which is well-
known in other Mammals, such as Bos.

THE PNEUMATIC SINUSES.

For the purpose of a special investigation of the pneumatic
sinuses we have sacrificed two of the skulls at hand, c and h, of
the latter, however, only the left half. Of the skull e the pneumatic
sinuses have besides been opened by chisel, the surface of
the skull being removed, and through transverse section etc. of
several of the other skulls we have obtained data contributing to
our knowledge of the pneumatic sinuses.

We begin by describing the sinuses in c and h, and then
proceed to a joint description of the pneumaticity in the Elephant
(cp. also p. 95 of the preceding).

Elephant c.

Left half of the skull (PI. 28 fig. 1, PI. 29 figs. 1 and 2, PI. 43,
PI. 45 fig. 1).

From the ethmoid issues a system of pneumatic sinuses which
may be described in detail as follows.

The caudal part of the nasoturbinal appears as a vault in
which are found two small sinuses, sinus V and I", the apertures
of which are both on the lateral side of the nasoturbinal. The
ventral and largest sinus extends even to the ventral apex of the
nasoturbinal. The rostral part of the nasoturbinal is also pneumatic
and in the object investigated containing no less than 4 small sinuses
. Most rostrally we see a rather high but narrow sinus lb',
elongating laterally and ending as a bulla rising from the bottom
of the sinus 8 a'. The aperture is placed about directly off the
middle and close behind the basal lamella of the 7. ectoturbinal,
c. 1 cm ventrally to the aperture of sinus 7 a'. Then follow two
small sinuses, a dorsal one with the aperture exactly laterally to
the nasoturbinal, and a little larger ventral one opening on the
maxillary bone directly ventrally to the nasoturbinal. Finally,
most caudad we find a small sinus ending in a slit-shaped, crescent
-shaped aperture; this opening is lying on the lamina lateralis
of the ethmoid, c. 1^ cm ventrally to the nasoturbinal in a
furrow on the lateral wall of the nasal cavity (see below).

Between the basal lamellae of the 1. and 2. ectoturbinals, close
below the lamina cribrosa, we see a small, round opening leading
into a quite small sinus V, of the size of a pea, in the frontal
bone, where it is completely covered by the sinus 6'.

Sinus 3', the rounded aperture of which is situated far upwards
between the 3. and 4. ectoturbinals, is a small sinus in the
deep part of the frontal bone, directly caudad to the sutural plane
between this bone and the nasal. The sinus consists of a medial
part, divided into several small sections which are mutually connected
; then it extends laterad as a very narrow compartment along
with and caudad to the above named suture, and from this compartment
issues a row of three prolongations, of which the lateral
and the middle one are so high that they rise like a pair of "bullae"
from the bottom of the sinus 6' (the middle, higher one, is 2 cm
in height) whilst the medial is so low as to be completely hidden
by the sinus 6'.

Between the 4. and 5. ectoturbinals there are two apertures,
most dorsally a rounded one leading into a very small sinus 4' in
the frontal bone, where it rises a little from the bottom of sinus 6',
whilst the sinus 4 a' is so small that it is completely hidden by
the same sinus.

Close below the lamina cribrosa, between the 6. and 7. ectoturbinals
, there is a rather long, oval aperture leading into a narrow
, low and short compartment which then expands in a large
sinus 6' occupying the greater part of the frontale and extending
a little into the parietale. It reaches right unto the septum sinuum
(it is here c. 5| cm deep), breaks through the sutural plane almost
midway between the frontalia and expands a little into the right
frontale. The sinus is divided into a larger medial part, rostrad
bordering on the sinus nasalis, caudo-laterad on the sinus 7', and
between these two sinuses it proceeds tapering into the lateral
part which extends further on in the frontale, where it wedges
in between the sinus 8 a' laterally and the sinus intermaxillaris
superior medially. The sinus 6' is already in this young specimen

1 In Elephas afrieanus there are also 7 endoturbinals, but only 19 ectoturbinals'
arranged in the following way: 1.—16. between 1. and 2. endoturbinals, 17.—18. between
2. and 3., and 19. between 6. and 7. endoturbinals.

1 The designations of the different sinuses are the same as in Paulli: Om Pneu-
maticiteten af Kraniet hos Pattedyrene, Kbhvn. 1899 (German traduction in Morph.
Jahrb. Bd. 28, 1899—1900).