DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 105 
process is but little free at its end (see also fig. 3., pg.) ; the fore part of each bone, 
above, runs inwards over the palatines and the two bones are toothed where their thin 
edges touch. 
Outside these bones, we see, in the distance, the orbital plate of the frontal (#1) with 
its large vascular hole, and at the margin of this space the jugal (j.), a considerable 
bone, broadened out where it overlaps the maxillary. It is, in turn, overlapped by the 
squamosal (sq.), whose jugal process passes a short distance beyond the jugal, and 
then, on its inside, at its root, we see the rather large glenoid facet (g/.f.) which is oval, 
the long axis forwards, but the fore part emarginate, having there a deep rounded 
notch. 
The squamosal can be seen a little in front of the glenoid cartilage ; laterally, it 
runs from its Jugal process, backwards, until we see it, after forming four gentle con- 
vexities and slightly converging, lie over the auditory capsule, ending beyond the 
stylomastoid foramen (VIL). 
The thickened postglenoid edge is separated from the beginning of the hollow, and 
somewhat pneumatic, part that covers the tegmen tympani. The inner margin is 
scooped, thin, and then thickens again before it ends as a scaly tract over the swelling 
in the ear capsule caused by the horizontal semicircular canal (see fig. 3, h.s.c.). 
Another superficial bone is seen inside the squamosal; this is the tympanic (@.ty.), 
it is a thinnish U-shaped tract, with a foot-shaped flange, in front, for protection of 
the processus gracilis of the malleus. This imperfect ring leaves a large space of the 
auditory capsule only covered by membrane on its inner side, and the rim of the bone 
lies a good distance behind the Eustachian opening (ew.). The membrana tympani 
(m.ty.) is much exposed, and the unossified manubrium (72.77/.) is seen running obliquely 
across it. 
The proximal, ossified part of the orbitosphenoid (0.s.), can be seen in the fundus of 
the orbit, with the optic nerve (IL.) running through, and the maxillary nerve (V*.) 
behind, it. A considerable tract of each alisphenoid (a/.s.) is seen between the ptery- 
goid and squamosal (sq.), and the large inferior branch of the 5th nerve (V*.) passes 
through a very large foramen ovale, which lies in the centre of the plate, but which 
is not quite bound in with bone on the outside. 
The large median beam, with the presphenoidal region unossitied, the basisphenoidal 
centre (b.s.), the basioccipital, and the whole occipital cincture will be described soon, 
as parts of the separated endocranium (Plate 15, figs. 1, 2). There is in this 
figure a small scale of bone seen in front of the stylo-mastoid foramen, and on the 
proximal part of the epihyal cartilage (e.hy.); this is the proper parosteal stylo- 
hyal bone (s¢./.), answering to that of Man, and of the Rabbit.* 
I have not found this superficial ossicle in any other kind of Edentate, and 
* Prorgessor FLowsr’s “ tympano-hyal”’ answers in a general way to this bone, but it lies deeper, and 
soon forms the ectosteal plate of a small patch of bone which is added to the “ opisthotic,” but belongs 
to the proximal part of the hyoid arch, where it has become confluent with the capsule. 
