3<D2 Elementary Biology. 



the para-sphenoid ; the walls are composed of cartilage and 

 the roof of two narrow plates closely united, the parieto- 

 frontal bones. Anteriorly the walls of the cylinder are 

 composed of a bony girdle, the sphenethmoid, while above 

 that bone and in front of the parieto-frontals, are two small 

 bones known as the nasals. Attached to the occipital ring, 

 one on either side, are the ear or otic capsules, composed 

 partly of bone, partly of cartilage, while the nasal bones 

 shelter the nasal capsules. The eye is not attached to the 



FIG. 164. -LATERAL VIEW OF THE FROG'S SKULL. (Milnes Marshall.) 

 FP L 



A, para-sphenoid ; AS, angulo-sphenial ; B, i, anterior and posterior horns 

 of hyoid ; H, body of hyoid ; c, columella ; D, dentary ; E, exoccipital 

 F, nostril ; FP, parieto-frontal ; L, exit of optic nerve ; M, maxilla 

 MM, mento-meckelian, or chin bone ; M', exit for fifth and seventh nerves 

 N, nasal ; o, prootic ; p, pterygoid ; P.M, premaxilla ; Q, quadrato 

 jugal ; R, exit for ninth and tenth nerves ; s, squamosal ; SE, sphen- 

 ethmoid. 



skull, but lies free on either side, midway between the ear 

 and nose. 



The upper framework attached to this box consists of a 

 number of narrow bones passing from the ear-capsule on the 

 one hand to the nose-capsule on the other, and forming 

 with the skull a bony ring round the eye. In front and on 

 the under surface of the skull lie four small bones, two rod- 

 like and stretching from the sphenethmoid outwards, the 

 palatines, and two triangular bones lying in front of the 

 palatines, the vomers, which have already been referred to 



