Mir PHYLUM CHORDATA :;i'.) 



or (literal 2)od- frontal [pt. nrh.) aitieulatiuiL,^ witli tliu I'roiital. Just 

 behind the postorbital is a supra-tcmiwral bone {supra t^), in close 

 relation to which are the 2wra -quadrate (sq) and squamo-Hal {supra, t^), 

 the former bending forwards and iipwnrds to form with the post- 

 orbital the xuprrinr icniporal arch. At the anterior extremity of 

 the snout is a median bone formed by the coalescence of the two 

 prcmaxillce {p. mx) ; this bears tlio four anterior teeth of each 

 side. On each side behind the prcmaxilla is the maxilla {max), 

 consisting- of two portions, an alveolar bearing all the rest of the 

 teeth, and a 'p<(latinc extending inwards on the roof of the mouth, 

 together with an ascending process articulating with the nasal and 

 pre-frontal above. Articulating behind with each maxilla is a 

 jvgal {ju), which forms the posterior half of the ventral boundary 

 of the orbit. The quadrate {qu) articulates movably with the 

 parotic process, and bears at its distal end the articular surface for 

 the mandible. 



In the anterior portion of the roof of the mouth, articulating 

 in front with the premaxilUe and maxilla3, are the vomers (vom). 

 Behind and embracing them posteriorly are the flat p)'^'^"^"^^-^ 

 {pal). The elongated pterygoids (pt.g) articulate in front with the 

 posterior extremities of the palatines : behind each articulates 

 with the corresponding liasi-pterijgoid proeess {has. p)tg) of the basi- 

 splienoid, and sends back a process which becomes applied to the 

 inner face of the quadrate. A stout bone wliicii extends between 

 the maxilla externally and the pterygoid internally is termed the 

 transverse hone or ccto-pterygoid {trans). Extending nearly veiti- 

 cally downwards from the pro-otic to the pterygoid is a slender 

 rod of bone, the epi-pterygoid {eol). 



The eohimella is a small rod partly composed of cartilage and 

 partly of bone, the outer end of which is fixed into the inner 

 surface of the tympanic membrane, while the inner is attached to 

 a small aperture, the fenestra, oralis, in the outer wall of the auditory 

 capsule between the pro-otic and the opisthotic. 



Certain depressions or fossse and apertures or foramina are to be 

 observed in the skull. The foramen magnum, the parietal foramen, 

 and the orbits have been already mentioned. The posterior 

 temporal fossa is situated on either side of and above the foramen 

 magnum, bounded above and externally by the rooting bones, and 

 on the inner side by the bones of the occipital region. The inferior 

 temporal fossa is bounded internally by the pterygoid, and is 

 separated from the palatine foramen by the transverse. The 

 laterrd temporal fossa, is the wide space in the side wall of the 

 skull behind the orbit ; the bony bar which limits it above is 

 the superior temporcd arch ; a bony inferior tcmpond or qudrafo- 

 jugcd arch is here absent. The tympano-eustachia.n fossa, 

 situated in the auditory region, is bounded by the bones of 

 that- region together with the quadrate. The posterior or 



