47^ THE RABBIT CHAP. 



h. sph. basisphenoid ; cotid. is wrongly lettered — cor points just below the_ condyle ; 

 fr. frontal ; int. pa. interparietal ; ju. jugal ; Icr. lachrymal ; max. maxilla ; nas. 

 nasal ; opt.fo. optic foramen ; o. spit, orbitospbenoid ; pa. parietal ; pal. palatine ; 

 pal. jita.w palatine process of maxilla ; par. oc. paroccipital process of exoccipital ; 

 pal. p. 7tiax. palatine process of premaxilla ; /. max. premaxilla^; peri, periotic ; 

 fit. pterygoid ; /. t.sq. post-tympanic process of squamosal ; j. oc. supraoccipital 

 sg. squamosal ; ty.biil. tympanic bulla ; vo. vomer ; zyg. max. zygomatic process 

 of maxilla. (From Parker and Haswell's Zoology.^ 



The upper jaw forms part of the facial region, which 

 encloses the olfactory chambers, and the lower jaw, consist- 

 ing of a single bone on either side, articulates directly with 

 the sides of the cranium without the intervention of a 

 hyomandibular, as in the dogfish (p. 422) or of a quadrate 

 cartilage, as in the frog (p. 44). The rest of the visceral 

 portion of the skull, representing the hyoid and first branchial 

 arch, forms the so-called hyoid bone, which is embedded in 

 the base of the tongue (Fig. 125, hy): 



The bones^ which form the walls of the brain-case are 

 arranged in three rings or segments, the middle and post- 

 erior of which are separated by the auditory bones (Figs. 

 123 and 122, A, perl). 



The posterior, or occipital segment, consists of three bones^ 

 which in the adult become completely united with one another. 

 The lower of these is the haslocclpltal (l>. oc), a flattened bone 

 bounding the foramen magnum below, and forming the 

 hinder part of the base of the skull and the lower part of 

 each occipital cond)'le {oc. c). The two exocclpltals {e. oc) 

 bound the foramen magnum at the sides, and form the 

 upper part of the occipital condyles : each is produced 

 downwards into a paroccipital process {par. oc) which fits 

 closely against the pc^terior surface of a swollen bone {ty. but) 

 to be described presently, which is produced into a tube 

 surrounding the auditory aperture (intd. me). The occipital 

 segment is completed above by the supraoccipital {s. oc) 



' In the following description, the membrane bones arc ilislinguished 

 by an asterisk from the cartilage bones. 



