ANATOMY OF BIRDS 



247 



The Hyoid Bone (Gr. letter i», Im = hy, e'So?, eidos, form ; Figs. 

 65-68, 72-74) is the skeleton of the tongue ; 

 a very composite structure, consisting of 

 several distinct bones, developed in the 

 second and third postoral visceral arches (see 

 Fig. G5, where ch and hh are the original ele- 

 ments of the second arch, making the basi- 

 hyal ^ and ceratohjal bones, and hhr, cbr, and 

 ehi; are the original elements of the third 

 arch, making the basihranchial, ceraiobranchial, 

 and epibranchial bones). The whole affair 

 is somewhat A" or H -shaped, lying loosely, 

 point forward, between the forks of the 

 lower jaw, with its long slender prongs curv- 

 ing up behind the hind head more or less ; 

 but it is not definitely connected with any 

 other bones of the skull. The connection 

 which exists between the hyoid and other 

 cranial bones in a mammal is in birds broken 

 by non-development of certain links of bone 

 developed in the mammalian second post- 

 oral arch, as the stylohyal, epihyal, etc. ; 

 though birds have a rudimentary stylohyal, 

 at least in the embryo, among the several 

 proximal parts of the second arch which form 

 the intricate bones within the ear-passages 

 (Fig. 67). The visible parts of a bird's hyoid 

 are usually : the body of the bone, basihyal 

 (bh, and Fig. 72, c), single and median, com- 

 monly quite short and stocky, sometimes long 

 and slender. The basihyal bears in front a 

 pair of ceratohyals {ch ; not shown in Fig. 72, 

 where they have been absorbed in b) usually 

 movably articulated with the basihyah They 

 commonly appear as little " horns " or pro- ^ „., _„ . . . 

 cesses of the next piece, the glossohyal (Fig. goose, nat. size ; by Dr. r. w. 



i-rr, i\ 1 \ • a i.- iU ^ Shufeldt, U.S.A. a, carti- 



7 2, b) or bone chietiy supportnig the sub- laginous end-piece of h, the 

 stance of the tongue. It may be a stout and I^^^^T^J^t.^. 

 apparently sing-le bone, as that of the 2;oose iiyaisor " lesser comua " ; c, 



n T \ J oi • r basihyal, movably articulated 



ngured ; but ottener appears as a pair of " ' ' 



slender bones, side by side, whose backward 

 ends are the ceratohyals. The glossohyal 

 may or may not bear at its fore end a car- 

 tilaginous tip, as in Fig. 72, a. All the 



^ Basihyal, etc. The word hyal, used ouly iu comi^osition, means the same as 



with &, and combined com- 

 pletely with d, basibranchial, 

 commonly called " urohyal ; " 

 c, ceratobranchial ; /, epi- 

 branchial; e and /are together 

 known as " thyrohyals," or 

 "greater cornua." 



