THE JAWS. 51 
8. Membrane bones of olfactory capsules. 
i, The nasals: two triangular bones on the dorsal 
surface of the anterior end of the head: the bases 
of the triangles are turned towards the middle 
line and meet one another in front, while their 
posterior ends diverge from one another and 
enclose, with the anterior ends of the fronto- 
parietals, a diamond shaped patch in which the 
sphenethmoid is visible from the dorsal surface. 
ii, The vomers: two triradiate bones on the ventral 
surface of the fore part of the head : each vomer 
bears at its inner and posterior angle a small 
group of pointed teeth, and forms the inner bound- 
ary of the posterior narial opening of its side. 
Fig. 9. The frog’s skull from the right side. 
A, parasphenoid: AS, angulosplenial: B, anterior cornu of hyoid: ¢, 
columella: D, dentary: E, exoccipital: F, nostril: FP, frontoparietal: H, 
body of hyoid: L, aperture for exit of optic nerve: M, maxilla: MM, mento- 
meckelian: M’, aperture for exit of fifth and seventh nerves: N, nasal: O, 
pro-otic: P, pterygoid: PM, premaxilla: Q, quadratojugal : R, aperture for 
exit of ninth and tenth nerves : S, squamosal: SE, sphenethmoid: T, posterior 
cornu of hyoid. 
3, The jaws: consist of two cartilaginous arches on each 
_ side, maxillary and mandibular, in connection with 
which cartilage and membrane bones are developed. 
Each arch meets and fuses with its fellow in the middle 
line in front; and the maxillary arches, forming the 
