SEC. IV 



ANATOMY OF BIRDS 



247 



The Hyoid Bone (Gr. letter v, hu = hy, effios, 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. 65, where ch and hh are the original ele- 

 ments of the second arch, making the lasi- 



?i and ceratohyal bones, and bbr, cbr, and 

 are the original elements of the third 

 arch, making the basibranchial, cerafobrcmchial, 

 and epibrmichial bones). The whole affair 

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

 point forwa,rd, 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, hasihyal 

 (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 basihyal. They 

 commonly appear as little " horns " or pro- 

 cesses of the next piece, the glossohyal (Fig. 



Pro. 72.— Hyoid bones of a 

 goose, nat. size ; iDy Dr. R. W. 

 Shufeldt, U.S.A. a, carti- 



rja i\ T. i..\a i- XT. iT onufeldt, U.S.A. a, carti- 



72, 0) or bone chiefly supporting the sub- laginous end-piece of 6, the 



stance of the tongue. It may be a stout and f£bf^T^,^$kcldte™to- 



apparently single bone, as that of the goose lyaisor "lesser cornua";c, 



p , ^, ° - ' , p basihyal, movably articulated 



ngured ; but oftener appears as a pair of with 6, and combined com- 



slender bones, side by side, whose backward ?J^:^'i^*^aUed^™i!'' 

 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 



^ Badhyal, etc. The word Tvyal, used only in composition, means tte same as 



ceratobranchial ; /, epi- 

 b'ranchial ; e and/are together 

 known as "thyrohyals," or 

 " greater cornua." 



