a eee Le Tl 
THE OSTEOLOGY OF AMIURUS CATUS; 285 
bone, lies the cartilaginous symplectic, in a perfectly dried skull, the 
fossa being empty and an interspace occurring between the quad- 
rate and the hyomandibular. The posterior border of the quadrate 
is contained in a groove on the preoperculum ; behind and above it 
articulates with the hyomandibular ; and above and in front with the 
metapterygord. 
7. THe Manpis-e, (Pl. IT., Fig. 1, Mn.) 
Consists of two portions, one on either side, united in the median 
line in front by ligament. Lach portion again consists of four parts. 
These are as follows :— 
(a) The dentary, constituting the anterior two-thirds of the bone 
and bearing numerous teeth. It is broader in front than behind, the 
teeth being arranged correspondingly, there being 5-6 rows anteriorly, 
tapering off to two rows posteriorly. The bone increases in height 
posteriorly, and is grooved on the inner surface for the reception of 
Meckel’s cartilage and the articulare. The under surface presents 
Six pores, openings for branches of the mucous canal which runs 
in this portion of the bone. 
(6) The articulare forming the posterior high portion of the bone, 
and presenting the articular surface for the quadrate. It encloses 
Meckel’s cartilage posteriorly. 
(c) Meckel’s cartilage, the remains of the primordial cartilaginous 
mandible. It consists of a rod of cartilage lying on the inner sur- 
faces of the dentary and articulare, its posterior portion being in- 
cluded within the latter. 
(dq) The angulare, fused completely with the articulare, being 
merely indicated as a small triangular nodule below the articular 
surface. 
The great size of the intermaxillaries and the limitation of the 
teeth to them, as far as concerns the upper jaw, are points worthy 
of notice. This is, of course, due to the specialization of the 
maxille for another purpose ; with the decrease in size of the lat- 
ter was an increase of the former. The intermaxille belong to that 
class of bones which are formed by the fusion of cement-plates of 
teeth. At first they are represented by a thin lamella of bone-bear- 
ing teeth, but by means of osteoblasts the ossification extends into 
the superjacent tissue in the form of trabecule which are, in their 
histological details, similar to the cement plates. 
