THE SKULL. 55 



and overlapping the hinder end of the spheneth- 

 moid. 



ii. The parasphenoid is a X shaped bone on the ventral 

 surface of the cranium ; its lateral processes 

 underlying the auditory capsules. 



2. The Sense Capsules are cartilaginous and bony capsules 

 which surround and protect the olfactory and auditory 

 organs ; they are fused with the cranium so as to form 

 parts of the skull. 



a. The auditory capsules are fused with the sides of the 

 posterior end of the cranium, to which they form 

 wing-like projections: they consist largely of cartilage. 

 i. Cartilage-hone of auditory capsules. 



The pro-otics are a pair of irregular shaped bones 

 in the anterior walls of the capsules, and forming 

 also parts of their roof and floor. 



h. The olfactory capsules are fused with the anterior end 

 of the cranium, and also with each other. They 

 consist very largely of cartilage, which is produced in 

 front into the rhinal processes. 



i. Cartilage-bone of olfactory capsules. The spheneth- 

 moid, as already noticed, extends forwards so as to 

 invade the olfactory region, but does not properly 

 belong to the olfactory capsules. 



ii. Membrane-hones of olfactory capsules. 



a. The nasals are 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 each other in front, while their 

 posterior ends diverge and enclose, with the 

 anterior ends of the frontoparietals, a diamond 

 shaped patch in which the sphenethmoid is visible 

 on the dorsal surface of the skull. 



/3. The vomers are two triradiate bones on the ventral 

 surface of the fore part of the skull : each vomer 

 bears in 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. 



