348 CHORDATA. 
and lies between the two orbits. Its front end is surrounded 
by a girdle bone, the sphenethmoid. Its walls are formed of 
cartilage, in the roof of which are a large anterior fontanelle 
Fig. 245.—VENTRAL VIEW OF Froc’s SKULL. 
Cartilage black, Bones white. 
Vomer. Premaxilla. 
Maxilla. 
Sphenethmoid, 
Parasphenoid. . 
Pterygoid. 
Quadrate. 
Prootic. Exoccipital. Columella. 
and a small pair of posterior fontanelles, as in the skate. 
The fontanelles are not seen, as they are covered up by a 
pair of large membrane-bones, the frontoparietals. ying 
Fig. 246.—DorsAL View oF Froc’s SKULL. 
Cartilage black, Bones white. 
Premaxilla. 
Maxilla. External Nas. 
Nasal. 
2 Sphenethmoid. 
Pt d. °P! 
er Frontoparietal. 
S iy 
sree Quadratojugal. 
RAS % 
Quadrate. 
Exoccipital. Prootic. 
under the cranium is a long dagger-shaped bone, the para- 
sphenoid. At the hind-end of the cranium is a pair of bones, 
the exoccipitals, each of which bears an occipital condyle. 
Anteriorly the cranial cartilage is continuous with the 
