304 MR. W. K. PARKER ON THE STRU CTURE AND 
own direction is backwards. Further back (fig. 4) the septum is increasing in height, 
and the retral processes of the trabecular horns are now much smaller; these slender 
laminz I propose to call the “recurrent cartilages”*. 
In the fifth and siath sections (figs. 5, 6, 6") there is no longer any distinction between 
the rudimentary prenasal cartilage and the completely fused portion of the trabecular 
bar, the lower part of the septum nasi; but as this bud-like wedge of cartilage (see 
Second Stage, Plate XXX. fig. 1, p.7.) never becomes vertical, having its apex downwards 
as in the Chelonians, still less protruded forwards as in its large counterpart in the 
Bird, the bony plates that appear as its splints are not superior as in the Bird, nor 
anterior as in the Chelonian, but ¢nferior. These plates are the premaxillaries, which 
appear in the Mammal below the snout (see also CALLENDER, Philosophical Transactions, 
1869, p. 166, Plate xrv. fig. 6, ¢, for its inferior position in Man). Yet in the Mammal 
the premaxillaries are related, as splints, more to the retral trabecular cornua themselves 
than to the arrested azygous cartilage impacted between them. So much of the alinasal 
cartilages as are depicted in the enlarged figure (fig. 6%, a/.n.) is a separate segment— 
the “appendix ale nasi.” The next section (fig. 7) is behind the first third of the septum 
nasi, where the rudiments of the ‘‘ hard palate” begin in front, the lips of which appear 
now on each of the padded bases of the septum, but are here far apart. The long 
cushion-like valvular mass in which the aliseptal folds (a/.s.) end and dilate is the early 
form of the inferior turbinal, which is not so sharply separate from the alinasal turbinal 
(al. tb.) as in the Bird. A sharp process of mucous membrane is seen above this on each 
side, where the aliseptal cartilages bend inward; this is the rudiment of the “ nasal 
turbinal” (see Huxxey, ‘ Elem. Comp. Anat.’ p. 248), which is but feebly developed in 
the Pig. In the thick mass which envelops the base of the septum two flat straps of 
cartilage are seen in section ; these are the “ recurrent lamin” (7.¢.c), and they are con- 
tinued in this stage back to that part of the septum which, ossifying earlier than that in 
front, gets the name of * perpendicular ethmoid” (see fig. 11). On each side of the lower 
palatal lip there is a rudimentary tooth-pulp shown in section; and above this, up to the 
nasal roof, the tissue is marked off from the skin and subcutaneous tissue; this is the 
granular nidus for the posterior margin of the premaxillary and the anterior margin of 
the maxillary. The detached piece of this section (fig. 7") is the fore end of the lower 
jaw with tooth-pulps appearing, and with a curious result of the great prognathism of 
the type, namely, complete fusion of the ends of the primordial mandibular rods— 
“ MECKELS cartilages (m/.c.).’ A section made near the middle of the septum (fig. 8), 
although answering on the whole to the 7th, shows the tip of the vomer (v.) anda very 
near approach of the lips of the hard palate, and, below (fig. 8“), the convergence of 
the mandibular rods and the fore end of a bony tract outside them; this is the dentary 
(d.); the tongue (¢g.) is here cut across. 
The ninth section (fig. 9) takes in part of the frontal wall, with the foremost part of 
* The “recurrent cartilages” are of great morphological importance; in future communications I hope to 
te} to) } to} } 
show their form and meaning in the Ophidians and in Birds, “ Passerines,” “‘ Hemipods,” the Rhea, &e. 
