OF THE SKULL IN THE COMMON SNAKE. 
401 
besides what lias just been noted, namely, the sectional views of the membranous 
bony tracts. 
The lsi section (Plate 30, fig. 2) shows the junction of the coalesced trabeculae with 
the inner laminae of the nasal roof to form the septum nasi ( s.n .). 
This section shows the utter simplicity of the olfactory cartilages, and how that the 
huge nasal gland and its bony capsules- — dish and cover — fill all the lower part of 
the nasal canal. 
These canals are nearly surrounded by cartilage, for the wall turns inwards, and 
then there is a floor piece formed by the upper labial (u.l.). 
In the 2nd section (fig. 3) the total arrest of the fore skull is shown ; there is 
nothing in the region of the hemispheres and eyeballs save the pair of elegant, 
rounded, solid trabecular rods (tr.). 
So, also, in the 3rd section (fig. 4). Here, however, we see two curious palatal 
papillae, such as I long ago showed to exist in the mouth of the Tadpole, and. which 
abound in the mouth of the Ammoccetes-larva of the Lamprey. In that case they are 
the rudiments of the armature of the sucking disk. 
In the 4-th section (fig. 5) we have the broadest region of the hemispheres (C la ) cut 
through, just where the carotid arteries ( i.c .) enter, and where the pituitary body (py-) 
is grafting itself upon the floor of the cavity of the infundibulum {inf.). 
As the trabeculae are bifurcated by the burrowing of the internal carotids, they 
appear in section as two cartilages on each side ; here the parietals (p.) form floor 
and wall to the brain cavity. 
In the 5th section (fig. 6) the mid brain is seen lying upon the hind brain (C 2 , C 3 ) ; 
the anterior ampullae are cut through {a. s c.), and the wall of the ear-capsule is seen 
to be imperfect on its inner face. This open part is the internal meatus. 
The section was made through the hind part of the “ posterior fontanelle,” and the 
basioccipital bone {bo.) had, in this case, just reached that open space ; there we see 
the deep concavity of the basal plate, and the swelling of the hind brain. 
Then, also, Meckel’s cartilage {mk.) is cut through, and also the angular and sur- 
angular {ag . , s.cig.) ; the floor of the face has been cut away, but the roof of the throat 
is shown. 
In the 6th section (fig. 7) we see the huge optic lobes resting on the hind brain 
(C 2 , C 3 , C 3a ) ; the section has been made through the middle of the ear-sac and the 
apex of the notochord. 
Here the basal plate is seen to be a large slab of cartilage, hollow above, convex 
below, and having the notochord lying upon it ; it is quite distinct from the ear- 
capsule on one side. 
The razor has cut through the anterior and horizontal canals {a.sc., h.sc.), and the 
vestibule {vb. ) ; the columella {co.) and Meckel’s cartilage, with the same splints as in 
the last {mn.), are severed. 
In the 7tli section (fig. 8) the perfect occipital ring is cut through, close behind the 
3 F 2 
