130 MR. W. K. PARKER ON THE STRUCTURE AND 
cartilage, which has, already, the form of the maxilla cuferior of a Mammal, for the 
coronoid, condyloid, and angular processes (cp., cd.p., ag.p.) ave present, although not 
yet ossified. The rest of this superficial tract will be described in the palatal aspect 
of the skull as the glenoidal facet for the articulation of this superficial and secondary 
mandible. 
The pharyngohyal element of the 2nd arch is already specialised into a stapes by 
growing as a ring to the stapedial artery, which traverses the auditory capsule exactly 
where this little, free nucleus, formed in the topmost part of the hyoid facial fold, is 
fitting itself into the secondary fenestra of the auditory capsule much as a Bird’s 
femur sets itself into the widely-perforated “acetabulum.” The next or epihyal tract 
(ehy.) is already confluent with the auditory capsule (Plate 22, fig, 3, e.hy., au.), close 
below the ampulla of the horizontal canal; the facial nerve (VIL) runs under the 
bridge formed by this junction. 
The ceratohyal (c.hy.) is divided through its middle, but is continuous with the 
epihyai above ; and this tape-like structure divides again near its base, developing a 
short subcrescentic segment, the hypohyal (h.hy.). 
The dilated, semicircular basal element (b.A.br.) rather belongs to the 3rd, or 1st 
proper branchial arch than to the hyoid ; it carries not only the hypohyals, but also 
the thyrohyals (¢.4y.), short out-bent, thick-ended rods, that articulate with the 
thyroid cartilage, and are the distal remnants of the abortive 3rd visceral arch. 
When once we are well assured of the points just given, all the rest of the 
Mammalian facial metamorphosis becomes easy to follow, and the “new things” thus 
produced become the most valuable diagnostics of the normal Mammalian face and 
jaws. 
Amongst the /ow Eutheria no better type than this can be found ; as a Mammal, the 
Hedgehog is very normal, yet it is much less specialised than several of its congeners, 
especially our other native Insectivora. 
First Stage (continued).—Vertically-transverse sections. 
This stage will now be illustrated by a complete series of vertically-transverse 
sections through all the tissues of the head. 
Ist Sectzon (Plate 18, fig. 1).—This is in front of the septum and catches the pro- 
jecting parts of the alze nasi (w/.n.), and the openings of the external nostrils (e.n.). 
2nd Section (Plate 18, fig. 2).—This is close behind the external nostrils in the 
narrow beginning of the nasal passages (n.p.). The septum here (s.7.) is but little due 
to the fore part of the crested intertrabecula, it is mainly formed by the confluence 
of the alinasal folds (a/.n.), back to back. This projecting part of the snout is grooved, 
above and below, through this union of the convex faces of the cartilages, which have 
made a partition thick above and thin below. Close to the openings of the nose the 
ale are most complete at the sides, and the lower parts are tucked in where they 
—” = 
CS a 
