HYOID 453 
(1) the “ Basihyal” (copula or corpus lingux) or unpaired middle 
portion, forming the basis of the framework ; 
(2) the “ Urohyal,” likewise unpaired, applied to the posterior 
end of the former, often wholly cartilaginous, and resting ventrally on 
the larynx, to which it is attached by muscles or ordinary connective 
tissue. In a few forms as Rhea, Sula and the Picide, it is absent ; 
(3) the “ Os entoglossum,” originally paired, but coalescing into an 
arrow-headed piece, attached to the anterior end of the basihyal, 
and lodged in the tongue proper. Equivalent to the ceratohyals, 
or anterior hyoid horns of Mammals ; 
CyYPSELUS. 
Dorsal view. 
Strrincops. Ventral view. Ruea. Dorsal view. 
bb. Basibranchial ; c. Corpus lingue or Basihyal; cb. Ceratobranchial ; ent. Os entoglossum ; 
u.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From the unpublished papers of Nitzsch, Giebel in 1858 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. Naturwissensch, x1. pp. 19-51, tabb. 
i.-vill.) the Hyoid bones of a great many birds, drawing attention 
to the taxonomic value of the modifications they present. Thus is 
shewn an unmistakable resemblance between Steganopodes and 
Tubinares, between Gulls, Guillemots and Divers, between Glareola 
and (Hdicnemus, Menura and the true Oscines, while on the other 
hand it is easy to distinguish the Hyoid apparatus of Panurus from 
those of the Paridx, and occasionally even closely allied species, as 
