HYOID APPARATUS, 53 
quadratojugal bone. The lower part of the arch also 
persists in part unossified as Meckel’s cartilage, which 
forms the base of the lower jaw, but is ensheathed by 
cartilage and membrane bones. 
a. Cartilage bones of mandibular arch. 
i, The angulosplenial: ensheaths the inner and lower 
surfaces of Meckel’s cartilage along the greater 
part of its length: near its hinder end it is 
produced upwards into the coronary process. 
i. The mentomeckelian: a small ossification in 
Meckel’s cartilage at the symphysis, ae., the 
union of the arches of the two sides at the chin. 
2. Membrane bones of mandibular arch. 
i. The squamosal: a T shaped bone, the body of 
which is closely applied to the outer surface of the 
quadrate cartilage. The posterior limb of the T 
is attached to the outer surface of the auditory 
capsule, and with the body of the squamosal 
helps to support the tympanic cartilage, a ring 
of cartilage surrounding the tympanic membrane. 
ii, The dentary: a flat bone covering the outer surface 
of the distal half of Meckel’s cartilage, as far 
forward as the mentomeckelian bone. 
4, The hyoid apparatus (fig. 9). Consists of the hyoidean 
arch and the remains of the branchial arches of the two 
sides, together with a median ventral plate—the body 
of the hyoid—which unites their lower ends together, 
and lies in the floor of the mouth. The hyoid appara- 
tus consists almost entirely of cartilage. 
a. The hyoid arch. 
i. The columella (figs. 9 and 10): the top of the 
hyoid arch ; forms a small rod, partly bone and 
partly cartilage, the inner end of which is in- 
serted into the fenestra ovalis—an aperture in 
the outer wall of the auditory capsule—, while 
the outer end is attached to the tympanic 
membrane rather above its middle. 
