DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 
233 
bend on the end of the maxillary, and is then cut away, so to speak, to receive the fore 
part of the ascending plate of the pterygoid (jpg.). The latter spreads out under the 
basisphenoid (b.s.), and is ankylosed with it, some distance behind and above the 
hamular process or hook. In this view the orbital region of the frontal (f) is seen in 
the distance, a large space existing between it and the bulging alisphenoid. On the 
right side of the figure the annulus (a.ty.) is shown ; it is well formed, convex 
outside, has a retreating, broad, notched, anterior crus, and a strong, crescentic hinder 
crus; both these crura are strapped on to a strong ridge of the squamosal, inside and 
behind the oval glenoid cartilage ( gl.c .). Round that facet the latter bone is thickened 
everywhere, though the inner and front part of that thickening is the stunted jugal 
process. The post-glenoid tract bends back against the bony auditory capsule and the 
inner edge is excavated, and united by a serrated suture with the tympanic wing of 
the alisphenoid ( al.s .), thus helping to form the tympanic cavity, as well as to enlarge 
the tegmen tympani. 
In the end view (fig. 5) the investing bones (i,p.,p., sq.) are but little seen; a side 
view of the septum of the olfactory organs (fig. 8) shows the large and remarkable 
vomerine series of bones. These are quite similar to those of Centetes (Plate 33); 
there is a large upper semitubular vomer, proper (v.), and two lesser semitubular 
bones sheathing it (v.). Behind, the main bone has attached to it a pair of postero¬ 
lateral centres (v".); the antero-lateral vomers are not distinct from the palatine 
processes of the premaxillaries ( px .). 
The endocranium of Hemicentetes. 
The snout (al.n., e.n.) is straight and bulges at the end and below; the nostrils are 
surrounded, except below, by a valvular fold of cartilage, they look downwards and 
forwards, and the antero-inferior face of the snout is oblique. The fore part of the 
septum nasi (fig. 7, s.n .) is obliquely oval, answering to the form and direction of the 
snout; the rest is a very low crest to a very solid and well-marked intertrabecula 
( i-tr .). Where the septum becomes ethmoidal there it rises into a low triangle, and is 
ossified as the perpendicular ethmoid ( p.e .); it has a kidney-shaped swelling with the 
“hilus” looking forward, just in front of its free inter-olfactory crest. The whole septum 
is rather saddle-backed ; it has a considerable cartilaginous tract behind, between the 
large bony plate and the presphenoid (p.s.). The latter tract is hidden from view in 
the lower aspect (fig. 1) by the main vomer (v.) ; the orbitosphenoids (o.s.) can be seen 
in the side view (fig. 3), they are perforated by the optic nerve (II.) as can be seen by 
looking forwards through the foramen magnum. In that figure the alisphenoids (al.s.) 
can be seen both above, where they form the curious thin dentate outer wall to the 
intersphenoidal passage, and also below, where the hinder openings of the alisphe- 
noidal canal (al.s c.) is seen a little in front of the foramen ovale (V.). That canal 
opens in front into the general cavity of the wide “ sphenoidal fissure ” (or passage). 
MDCCCLXXXV. 2 H 
