THE SKULL. 49 
a semicylindrical transverse piece of bone attached to the 
caudal margin of the coronoid process. It articulates with the 
mandibular fossa of the temporal bone. 
Hyoid Bone. Os hyoideum (Fig. 38 and Fig. 104).— 
The hyoid bene forms the support for the tongue and gives 
origin to muscles passing to the Z 
tongue and larynx. It also 
supports the thyroid cartilage 
(Fig. 104, 1). 
It consists of a transverse 
bony bar, the body (Fig. 38, a) 
and of two cornua or horns yy, 38.—Hyorp Bong, Dorsat View. 
attached to each end of the az, body; 4, ¢, d, e, cranial cornu; /, 
bod caudal cornu; 4, ceratohyal; ‘, epihyal; 
y: d, stylohyal; e, ‘tympanohyal; f, thyro- 
The cranial cornu (lesser hyal. 
cornu of human anatomy) i is the longer (Fig. 38, d-e). Each 
arises from the cranial face of the body at its lateral end, curves 
laterad, and then caudodorsad. It consists of four bony pieces 
movably united by cartilage. 
The terminal piece is the tympanohyal (¢); it is imbedded 
in the tympanic bulla just ventrad of the stylomastoid foramen. 
It is not therefore seen attached to the cornu after the latter 
has been separated from the skull. The other pieces become 
successively shorter toward the body, and are called stylohyal 
(d), epihyal (c), and ceratohyal (2). 
The caudal cornua (/) (greater cornua of human anatomy) 
arise from the ends of the body. Each consists of a single 
piece of bone, the thyrohyal (/), which passes caudolaterad ; 
its free end is united to a process of the thyroid cartilage (Fig. 
104, 1). 
The Skull as a Whole.—In the following description of the 
skull as a whole the mandible, hyoid, and ear-bones are not 
included. 
The skull forms a bony box which contains the brain and 
is produced craniad into the facial portion which encloses the 
nasal cavity and forms the framework of the face. 
In dorsal view (Fig. 39) the skull presents a smooth con- 
vex surface, broadest caudad, with the two zygomatic arches 
