166 
MR. W. K. PARKER OK THE STRUCTURE AND 
zygoma is imperfect, a tract of fibrous tissue tying the minute quadrate style to the extre- 
mity of the maxillary (Plates VII. & VIII., m%., qu.). 
If the relations of the maxillaries to the endoskeleton be considered (Plate VII. & VIII., 
m.x .), it will be seen that they are rather applied as splints to the nasal capsule than to 
the pterygo-palatine bar ; this relation to the nasal sacs is still more evident in the pre- 
and septo-maxillaries. 
But even the maxillary itself is applied persistently as a splint, in front, to the poste- 
rior spur of the bifid “ snout-cartilage.” Since the last stage but one (fifth) the nasal 
region has ungone a remarkable series of changes, and these not easily understood. I 
have, however, studied this metamorphosis very carefully, both in the small common spe- 
cies and in other and larger types. The condition of things in the fifth stage must be 
kept before the eye, and then the various illustrations in this (seventh) can be read off. 
The more enlarged figure of the anterior half of the primordial skull (Plate VIII. 
fig. 11) shows the appearance of the nasal labyrinth from above, after the removal of the 
bony plates. Here, this part of the skull shows that the trabeculae have become nearly 
lost in the general cartilaginous growth, and that an inturned lamina from the lateral 
walls is continuous with a growth from the posterior edge of the ethmoid ( eth .). But if 
this figure be compared with its counterpart of the fifth stage (Plate VII. fig. 2), it will 
be seen to what an extent cartilage has been developed around the nasal sacs. The 
septum nasi (s.n.) has now grown to the front of the face ; and from its right and left 
edges above, and also from the anterior edge of the transverse ethmoidal wall, there has 
been developed a continuous roof of cartilage to the nasal sacs. Sectional views explain 
this; for the dotted line of the fifth stage (Plate VI. fig. 10, al.s ) is now an elegant arch 
of cartilage (Plate VII. fig. 6, al.s.). 
But the septum is not only continuous with the roof ; a floor has been formed by the 
thinning out of the trabeculfe and their coalescence with the inferior edge of the septum 
(Plate VII. fig. 6, tr ., s.n.). In this latter figure the septum is thickened below its 
middle; this is where the septal outgrowths (to be described in the last stage) terminate 
posteriorly. 
The ends of the trabecular horns can just be traced in this more advanced stage as a 
pair of emarginate outgrowths, “ snout-cartilages” (Plate VII. fig. 11, sn.c.), each pro- 
jecting outwards from the front angles. 
The position of these processes is at the upper surface, although in the former stages 
the trabeculae turned downwards (Plate VII. fig. 1, tr .) ; but they have changed their 
direction, as may be seen in the palatal figure (Plate VIII. fig. 2, s.n.l.), where the sub- 
nasal lamiiue, or outspread trabecular horns, are seen to turn upwards behind the pre- 
maxillaries (p.mx). Each snout-cartilage forms a valvular process over the external 
nostril (v.e.n) in front of which it lies. But the external nostril (Plate VII. fig. 11, e.n.) 
is largely embraced by a peculiar development of the laminar roof. On the inner edge 
of the opening the aliseptal plate (al.s.) ends free; that free edge is then curled 
