76 MR. W. K. PARKER ON THE STRUCTURE AND 
the vomerine bones and cartilages (fig. 10) are from dissections of the latter, more 
developed, young; this will account for some differences of form in the parts. 
The complete /ongitudinally vertical section, made a little to the left of the 
mid-line, shows almost perfect ossification of the endoskeletal part of the skull, proper, 
with no appearance of bone in the internasal region. That region is very short in 
proportion to the long cranial cavity, which, itself, is remarkable for the large 
development of the supraoccipital (s.o.) and for the peculiarly low position of the 
whole of the double sphenoid, reminding the observer of the skull of Serpents. The 
delicate decurved snout has the familiar fenestra (7.7,f) in the fore part of the septum 
nasi (s.7.) between the external nostrils. The JAcopson’s, or recurrent, cartilage 
(re.c.)* is cut across on the left, but that of the right side is seen under the septum nasi 
(see also fig. 10). The whole septum (p.e., s.v.) is rather high in proportion to its length ; 
its thick intertrabecular base has an arched or concave outline, but the top of the crest 
or partition is convex for some distance, and then drops rather suddenly towards the 
snout. The descending margin of the middle ethmoid (p.e.) is somewhat crested (the 
crista galli) and grooved by the olfactory filaments; the cribriform plate (below c7.p.) 
cannot be seen in this view; the partition hides it. Here” the presphenoidal bony 
tract (p.s.) is now almost complete through the fusion of the orbitosphenoids, which 
have long ago lost their large upper cartilaginous tract joining on to the supratemporal 
crest, and the supraoceipital. 
The upper part of the orbitosphenoid only can be seen, and half the optic foramen 
(II.); that wing has its margin first descending and then rising into a short lobe in 
front of the sphenoidal fissure (V'*)). The alisphenoidal (a/., vead al.s.) lies still further 
out of sight, being thrust outwards as well as downwards (see fig. 1); its upper edge 
is notched gently, here, and the foramen ovale (V*.) is below the angular process that 
divides the notches (see also fig. 9). 
The cartilage between the pre- and basisphenoids (p.s., b.s.) is longer than that 
between the basisphenoid and basioccipital (b.0.) ; and the latter tract is high, being 
part of the postclinoid wall. This is thick now, being composed of part of two bones 
and the intervening cartilage, but in the adult the “sella” becomes more scooped, and 
the postelinoid wall is thin and curls forwards. The shorter presphenoidal tract 
of bone is twice as thick as the basal pieces behind ; the basisphenoid is the longest 
of the three. The internal carotid artery (/.c.) enters the skull nearer to the mid-line 
than in Eutheria, generally, but its entrance is normal; its internal continuation, 
forwards, is large, and lies in a very definite groove over the junction of the base 
and ala. 
The exoccipitals (¢.0.) have a considerable parting of cartilage, yet, between them 
and the basal plate (b.0.); the latter is notched in a crescentic manner, twice, first for 
the cochlea, and then for the exoccipital. A definite tract of cartilage still separates 
* The line from 7e.c. is wrongly directed to the premaxillary ; the anterior vomer (see fig. 10, v’.) is 
not lettered. 
