140 MR. W. K. PARKER ON THE STRUCTURE AND 
The end view (Plate 17, fig. 6) shows the roughly-oval interparietals, and the hind 
part of the parietals and squamosals (/.p., p., sq.) as they fit on to the auditory and 
occipital regions of the endocranium. 
But a lower view of the upper palate, after the hard palate has been removed 
(Plate 17, fig. 8), shows three more investing bones, namely, the front paired vomers 
(v’.), and the vomer, proper (v.). 
These paired bones are quite distinct from the palatine processes of the premaxil- 
laries, and are delicate, narrow laminze, with an outside hook in front ; they are placed 
vertically inside the recurrent cartilages (re.c.) and JACOBSON’s organs. 
Wedging in between their hinder part we see the narrow, bifid fore end of the main 
vomer (v.), which is roughly carinate in its fore half, and then flattens out, and is 
alate in its hind half where it is applied, right and left, as an ethmoidal splint, serving 
to bind the right and left floors of the nasal labyrinth together, as in Passerine 
Birds ; this upper junction of the right and left halves of the face has been called 
“ (Kgithognathism,” because of its peculiar development in Passerine Birds. 
Eidocranium of Second Stage of Erinaceus europeus. 
In the figure just referred to (Plate 17, fig. 8) we see the lower view of the alinasal 
cartilages (a/.7.) and the outer nostrils (e.7.). Constricted suddenly, these parts give 
off the neck of the curious, tongue-shaped recurrent cartilage (re.c.), which at its 
fullest part grows quite round Jacopson’s organ (see Plate 18, fig. 5). Behind these 
the floor of the nasal capsule, under the “ middle turbinals” (pc.c., the “ precurrent 
cartilages”), is partly shown, and then the narrow, unossified mesethmoidal (p.e.), and 
presphenoidal region (p.s.), and the very wide, ossified basisphenoidal (b.s.). This 
bony plate is transversely oval and is perforated in front; this hole is the pituitary 
space (py.). 
In the /ower view (Plate 17, fig. 3), behind the hard palate, the endocranium is well 
shown ; it is a broad osseo-cartilaginous structure. At the mid-line the presphenoid 
and basisphenoid (p.s., b-s., also shown in fig. 8) come into view, but the latter is partly 
hidden by the pterygoids ( pg., pg.c.), outside which the base of each alisphenoid (a/.s.) 
swells into an egg-like process (e.pg., or “external pterygoid”), much more distinct, 
now, than in the first stage (fig. 1).* Outside this swelling the cartilage is largely 
ossified as the alisphenoid (a/.s.), which is perforated nearer its hinder, than its fore, 
margin, by the 3rd branch of the 5th nerve (V*.); the rest of this nerve (V2) 
escapes through the sphenoidal fissure. 
The outer part of the orbitosphenoidal bony centre (0.s.) is just seen in front of the 
* This part is similar to what is seen in the embryo (uterine) of Didelphys, and the counterpart of 
which does develop even in some Insectivora (e.g., Rhyncocyon, Plate 36, fig. 5) into an “ anterior 
tympanic recess,” or alisphenoidal bulla; this, however, in the Hedgehog becomes the external pterygoid 
plate; a part which, in Kangaroos, co-exists with the tympanic wing of the alisphenoid. 
