HYOID 



453 



(1) the "Basihyal" {copula or corpus linguai) or unpaired middle 

 portion, forming the basis of the framework ; 



(2) the " Urohyal," likewise unpaired, applied to the postei-ior 

 end of the former, often Avholly cartilaginous, and resting ventrally on 

 the larynx, to which it is attached by muscles or ordinary connective 

 tissue. In a few forms as PJica, Sula and the Piciclx, it is absent ; 



(3) the " Os cntoglosmm" originally paired, but coalescing into an 

 arrow-headed piece, attached to the anterior end of the basihyal, 

 and lodged in the tongue pi'oper. Equivalent to the ceratohyals, 

 or anterior hyoid horns of Mammals ; 



Cypselus. 

 Dorsal view. 



Stringops. Veiitoi view. Rhea. Dorsal view. 



bh. Basibrancliial ; c. Corpus linguse or Basihyal ; ch. Ceratobranchial ; cut. Os entoglossum ; 



ii.h. Urohyal. 



(4) a pair of "Thyrohyals," homologous with the posterior 

 hyoid horns of Mammals ; and, as the most developed pair in Birds, 

 commonly called the "Hyoid Horns." Each of them consists of 

 two or three pieces, placed end to end, of which the basal one articu- 

 lates upon a facet of the posterior lateral corner of the basihyal. 



From the unpublished papers of Nitzsch, Giebel in 1858 

 described and figured {Zeitschr. ges. Natunvissensch. xi. pp. 1 9-5 1 , tabb. 

 i.-viii.) the Hyoid bones of a great many birds, drawing attention 

 to the taxohomic value of the modifications they present. Thus is 

 shewn an unmistakable resemblance between Steganopocles and 

 Tnbinares, between Gulls, Guillemots and Divers, between Glareola 

 and (Edicnemus, Menura and the true Oscines, while on the other 

 hand it is easy to distinguish the Hyoid apparatus of Panurus from 

 those of the Paiidx, and occasionally even closely allied species, as 



