OF THE SKULL IN THE COMMON SNAKE. 
405 
The opisthotic (op.) ensheaths the back face of the cochlea, forms the back margin of the 
fenestra ovalis, and forks over the fenestra rotunda nearly enclosing it (fig. 5, op.,fr .) ; 
but this part is left unfinished, and the fenestra rotunda does not open into the cochlea.'"' 
The opisthotic takes in the ampulla and three-fourths of the arch of the posterior 
canal, which runs up in its hinder edge, close to the exoccipital ; its lower margin 
barely reaches the basioccipital. 
The epiotic ( ep .) is wedge-shaped as seen from without (fig. 4) ; pyriform as seen 
on the inner side ; and oblong as seen from above. 
It takes in the contiguous fourths of the anterior and posterior canals, and their 
common “sinus;” its inner margin, above, slightly overlies the superoccipital ; its 
anterior edge is flanked by a process of the parietal (p.) now making the roof. 
The sub-reniform stapedial plate is one, both in its cartilaginous, and in this its 
ossified condition, with the columella (co.). I shall describe it with that element. 
The alisphenoicl ( al.s .) is planted upon the basisphenoid (hs.) and props up the 
prootic ; it is square now, having closed upon the first passage (for the first and second 
divisions of the 5th nerve, 5 1 , 5 2 ), and is notched behind for the third branch (5 3 ). 
These two passages are similar to the foramen ovale and foramen rotundum of 
human anatomy ; but the foramen rotundum here takes two parts of the nerve. 
The basisphenoid ( bs .) does not trespass further forwards along the trabeculae than 
to the front of the circumscribed pituitary space ; the bone has floored this space, and 
a cavity for the pituitary body exists above this secondary floor. 
Just above the carotid passage ( i.c .) the parietal (p.) is seen mounting up and 
creeping over the prootic ; on the inside (fig. 3) this bone projects strongly inwards in 
front of the auditory capsule and behind the optic lobes. 
The frontal (f.) is meeting its fellow above, but there is a considerable space 
unossified between it and the parietal laterally ; at the bottom of this fenestra the 
small trilobate orbito-sphenoid (os.) is seen above, and a little in front of, the optic 
nerve (2). The highest part of the carinate parasphenoid (pa.s.) is seen under and 
between the optic passages ; it is pointed in front and spatulate behind. 
The septum nasi (fig. 3) has been removed, and the olfactory cartilage (ol.) is seen 
from the inside ; postero-inferiorly we see a crescentic section of the reniform nasal 
gland (n.g.) covered by the septo-maxillary (s.mx.), floored by the vomer (v.), and 
having a large labial (u.l.) attached to its duct. 
Behind the vomer we see the inner nostril, and in the front of the face the pre- 
maxillary (px.) is cut through. 
The cartilaginous parts in front of the pituitary space have not altered since the 
last stage, and only alter in size afterwards. 
There is nothing new to mention in the palato- maxillary series of bones, but the 
mandible is at an instructive stao'e. 
* In a large Boa, from Demerara, I find no in ter-fenestral bar of tire opisthotic ; in Python sehce it exists, 
as in our native Ophidia, 
