un 
DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 22 
from behind, protected by a wing of bone in the true coronoid region, and the 
remarkable thickness, roundness, and solidity of the ramus is also shown. 
The lower view (Plate 21, fig. 1) shows a large pyriform tract, two-thirds of the 
whole inferior area, covered with superficial bones. The premaxillaries (px.) have a 
considerable dentary edge, and long, slender, compressed palatine processes. Each 
large maxillary (mx.) shows on this face three tracts, first, the series of alveoli, 
expanding from before, backwards; then the outer part of the palatine plate wrought 
into subtransverse ridges, and hollow with perforations ; and, close to the mid-line, a 
narrow tract, on a higher level. The two halves of the palatine plate end, in front, as 
spikes, the inner binding on the palatine process, and the outer on the dentary 
region, of the premaxillary. The inner tracts run short behind, the palatines (pa.) 
wedging in, in an irregular manner; the outer reach as far backward as the alveolar 
walls, binding strongly on the outer face of the open part of the palatines. The rough 
splintery fore part of the palatine plate of the palatines is split for some distance, 
and then towards the transverse ribbed edge, behind, shows the posterior palatine 
foramen (p.p.f.). Where the nasopalatine passages open, there both at the middle part 
and the sides each palatine bone is thick and solid; and then, suddenly thinning out, 
they bind on the small subparallel blunt-hooked pterygoids (py.); the pterygoid 
fossee are very indefinite. 
Over the opening of the nasopalatine canal the vomer (v.) is just seen in its 
hinder part ; and on the right side of the figure the annulus (.ty.) is shown, with its 
thick twisted anterior, and its sharp posterior, crus. The orbital plate of the frontal 
(f) is seen in the distance, and the squamosal (sq.) shows its obliquely oval glenoid 
facet (gl.c.), its stunted jugal process, and its short, strong, three-limbed postglenoid 
tract, with the postglenoid pneumatic foramen, close to the glenoid cartilage. 
On the hinder face of the skull (fig. 4) we get an imperfect view of the parietals, 
interparietals, squamosals, and tympanies (p., @.p., sq., @.ty.). 
On the inside of the skull, with the septum (s.n., p.e.), perfect, and shown from its 
left face, we get an instructive view of the investing elements of the skull. In front 
we see the nasals (n.) above, and the palatine process of the premaxillary (p.pz.) 
severed from its body below; and behind it, at the lower edge, the palatine plate of 
the maxillary and palatine (p.me., pa.), and the free retral hook of the pterygoid 
(pg.), growing from its ascending plate. 
Above, the frontals (f.), at their edge, and in their orbital region, and the parietals 
and interparietals (p., i.p.); the imbrication of the parietal over the frontal is very 
great; that of the squamosal (sqg.) below, over the parietal, is very moderate ; over 
this latter squamous suture the elegant furrow for the lateral sinus (s.c.) is well seen. 
But the most remarkable of all the investing bones still remain to be described, and 
are best seen in this view; these are the large vomers (Plate 33, fig. 5, v., ’., v”.). In 
the earlier stage (Plate 32) I failed to find a distinct anterolateral vomer ; this bone 
appears to be connate with the palatine process of the premaxillary, as in some other 
MDCCCLXX XV. 2G 
