SKELETON. 19 
In other ganoids (holosteans and crossopterygians) the skull is much like that 
of the teleosts, differing in the extension forward of the cranial cavity. There are 
Fic. 78.—Median section of skull of mackerel (Scomber) after Allis. For letters see fig. 68. 
one (Amia) or two (Polypterus) gular bones developed between the rami of the 
lower jaw, and in Polypterus parietals, frontals and nasals fuse with age, and there 
are numerous small bones in the cranial roof, developed along the lateral line 
canals. Amia has several splenials in 
the lower jaw. 
TELEOSTS (fig. 76-80) have a consider- 
able range of skull structure. In the lower 
groups like siluroids and cyprinids, the 
chondrocranium is largely persistent and 
the cranial cavity extends into the eth- 
moid region as in the higher ganoids. 
In other teleosts the trabecule are ap- 
proximate between the orbits (tropibasic) 
and develop a thin interorbital septum 
which limits the anterior ends of the 
cranial cavity. The cartilage bones are 
more numerous. All four occipitalia are 
present, the occipital condyle being formed 
by basi- and exoccipitals. Basi-, ali-, and 
orbitophenoids occur, and besides ecteth- 
moids a pair of mesethmoid ossifications. 
In the otic capsule there are usually 
pterotic and sphenotic ossifications. 
The cranial roof is largely formed by 4 
the frontals and parietals, the latter fre- 
quently separated by a strong process of 
the supraoccipital. Several of the car- 
tilage bones are visible from above. The 
roof of the mouth is formed by the large 
parasphenoid andthe vomers. Premaxil- 
faries (rarely lacking) and mazxillaries 
Fic. 79.—Dorsal view of skull of mack- 
form the upper jaw, both usually bearing erel, Scomber, after Allis; letters as in fig. 68 
