Chap. VIII.] THE SKELETON. 149 



This may be compared with the dental formulae of the cat, 

 the dog, and man, all of which have canines : 



, 3-3 1-1 3-3 1-1 



Cat, i. ff c. r - r p. m. _, m. ^ =30. 



3-3 1-1 4 4 2-2 



Dog, i. ^ -, c. j, p. m. j- , m. , =42. 



O O 1 1 T: 'x O O 



99 11 99 3 ^ 



- /r " """" " *- J- ^ ^ <-' *-* or* 



Movi -i v\ -ry iyi -?/ 



an > h 2^2' 1-1' P< 2-2' 3-3' 

 (7.) r/ze jEfyoid. This bone, developed from one of the visceral 

 arches, consists of a stout body or lasi-liyal (Fig. 44, D., b. h.), 

 small anterior cornua (a. c.), and larger posterior cornua (p. c.). 

 It lies in the root of the tongue. In the dog the anterior 

 cornua are longer, and consist of three elements. 



(B.) The Fowl's Skull. In the skull of an adult fowl, several 

 years old, the bones of the brain-case, and some other parts, 

 become so closely ankylosed, and completely fused, that it is 

 impossible to trace the sutures. In the skull of the young 

 chick, under a month old, some of the bones have not begun to 

 ossify. In the skull of a fowl some six months old, while some 

 of the bones are already ankylosed, the ossification of the 

 pre-sphenoid has not commenced. It will be convenient to take 

 for description the skull of a recently hatched chick, and the 

 skull of an adult bird. Fig. 48 gives a side view and ventral 

 view of the adult skull, the positions of some of the obliterated 

 sutures being dotted in. 



(1.) The Brain-case. This is rounded above and posteriorly, 

 but much encroached upon by the large orbits. In the chick 

 the basi-occipital, ex-occipitals, and supra-occipital are distinct ; 

 but in the adult they fuse with each other, and with the other 

 bones of the brain- case (b.o., e.o., s.o.). There is a single occipital 

 condyle, hemispherical and grooved dorsally. Anterior to the 

 basi-occipital is the basi-sphenoid. This bone is not, however, 

 visible in B., since it is hidden by a large expanded basi-temporal 

 bone (b.t.), at the anterior ends of which are the openings of the 

 Eustachian canals. The ali-sphenoids (48, A., a.s.) form part of 

 the anterior wall of the brain-case. Each sends out a strong 



