450 ZOOLOGY SKCT. xiii 



and that of the Pigeon is in the mode of connection of the lower 

 jaw, which in the former articulates directly with the skull — the 

 quadrate, through which the union is effected in the Pigeon, being 

 apparently absent. Certain large apertures which are distinguish- 

 able are readily identified with the large openings in the skull of 

 the Pigeon. In the posterior wall of the skull is a large rounded 

 opening, the foramen magnum, flanked with a pair of smooth, 

 rounded elevations or condyles for articulation with the first 

 vertebra, these obviously corresponding to the single condyle 

 situated in the middle below the foramen in the Pigeon. A large 

 opening, situated at the end of the snout and looking forwards, 

 obviously takes the place of the external nares of the Pigeon; 

 and a large opening in the roof of the mouth leading forwards to 

 the external nasal opening, plainly represents, though much wider 

 and situated further back, the internal or posterior nares of the 

 Pigeon ; while the rounded tubular opening {and. me.) situated at 

 the side of the posterior part of the skull, some distance behind 

 the orbit, is evidently the same as the auditory aperture of the 

 Pigeon. 



Surrounding the large opening of the foramen magnum are the 

 bones of the oceipiital region of the skull, the supra-, ex- and lasi- 

 occipitals. The first of these (s. oc.) is a large plate of bone whose 

 external surface is directed backwards and upwards, and elevated 

 in the middle into a shield-shaped prominence. The exoccipitals 

 lie at the sides of the opening, and each bears the greater part of 

 the somewhat oval prominence ot. condyle with which the corre- 

 sponding surface of the atlas or first vetebra articulates. Each is 

 produced below into a process called the paroccipiital (par. oc.), 

 closely applied to the tympanic bulla. At the end of this, imbedded 

 in the tendon of a muscle — the stylo-glossus — is a small bony rod 

 the stylo-hyal. A small aperture, the condylar foramen, situated 

 below the condyle, is for the passage of one of the cerebral nerves, 

 the hypoglosscd. The hasioccipital is a median plate of bone, almost 

 horizontal in position, which forms the floor of the most posterior 

 part of the cranial cavity ; it bears the lower third of the occipital 

 condyles. All these four bones of the occipital region are in the 

 adult Rabbit united together to form the single occipital lone. 

 Articulating in front with the basioccipital, but separated from it 

 by a plate of cartilage, is a plate of bone, also horizontal in position, 

 which forms the middle part of the floor of the cranial cavity. 

 This is the Ictsisphenoid ; it is perforated at about its middle by an 

 oval foramen — ihe pituitary foramen — and on its upper surface is a 

 depression, the sella turcica, or pituitary fossa (Fig. 1083, s.t.), in 

 which the pituitary body rests. In front of it is another median 

 bone of laterally compressed form, the presphenoid, with which it 

 is connected by cartilage, the removal of which leaves a gap in 

 the dried skull ; the presphenoid forms the lower boundary of the 



