132 
MR. W. K. PARKER OK THE STRUCTURE AND 
across on each side ol the cartilage, and in the lower skin the bristles show their 
bulbs. 
5 th Section (Plate 3, fig. 5).—Here the septum (s.n.) is deepening, and its intertra- 
becular base is less bulbous. The nasal labyrinth has thicker walls, and besides the 
expanding rudiment of the inferior turbinal ( i.tb.), further up, the pointed fore end of 
the nasal turbinal ( n.tb .) is cut across; a crypt is seen below it, and below the 
inferior turbinal. The skeletal parts that protect Jacobson’s organs (j.o., rc.c, v.') 
are larger here, and the cartilage forms a complete tube for a short distance; above 
are the nasals (ft.) ; at the sides, the bony laminae belong to both the premaxillaries 
(px.) and maxillaries. 
Below, the basimandibular cartilage ( b.mn.) is depressed; close in front of the 
Meckelian rods, right and left, a tooth-pulp ( t.) is seen. 
6th Section (Plate 3, fig. 6).—The septum (s.n.) is now much higher, and the bulb at 
the base much less ; the side wall is very thick, for here the nasal turbinal inside 
(al.sp.) is beginning to clear itself of the wall; below it the inferior turbinal rudiment 
is still seen. Here and there a mucous crypt is seen, and here Jacobson’s organ 
(j.o.) lies in a fold of the recurrent cartilage (rc.c.), behind the closed part, and behind 
the front-paired vomers. The nasals and maxillaries ( n.,mx.) now show more clearly, 
and the latter are developing the diploe, and are giving off the palatine plate. 
Below, the dentary (cl.) appears, outside the distinct large oval section of each 
Meckelian rod (rnk.). 
7th Section (Plate 3, fig. 7).—This section shows several new things. The deep 
septum (s.n.) is cut through at the junction of the septum nasi, proper, and the 
perpendicular ethmoid, the part that becomes solidly ossified in Mammals, in the true 
olfactory region. Under it the median vomer (v.) is seen, and Jacobson’s organs 
are small at this their hind part. The nasal passages (n.p.) are now becoming very 
complex or labyrinthic ; this is due to the greater development of the various turbinal 
folds, now that the section is through the proper olfactory region. The nasal turbinals 
(n.tb.) are, here, sharp and turned outwards at their free edge, whilst at the sides the 
wall is giving off new buds, and the inferior turbinal (i.tb.) is dying out. A remark¬ 
able free cartilage (m.tb.), oval in section, is seen in the principal cavity, covered with 
a mass of tissue, like the rest of the mucous and submucous lining. This is a 
process which grows forwards from the lower part of the labyrinth, from the region of 
the middle turbinal. It is large, here, but much larger in Orycteropus (see Plate 15, 
fig. 1), in which I have called it the precurrent cartilage (pc.c.). The vomer (v.), the 
nasals and maxillaries (n.,mx.) are well seen here. 
8th Section (Plate 18, fig. 8).— In this partial section the labyrinth is cut through 
just in front of the great olfactory fossae ; the perpendicular ethmoid (p.e.) has a 
submoniliform outline, due to three successive bulgings. The rudiments of the 
turbinal outgrowths are seen here, namely, the upper and middle turbinals 
(u.tb., m.tb.), and outside the latter, and just distinct from it, the thick trihedral 
