SKULL AND PECTORAL GIEDLE. 415 



angular, between this and the angular, as 

 far as the articular. 



e. The splenial is a thin lamina of bone, applied 

 to the inner surface of each ramus of the 

 jaw, along the middle half of its length. 



. The columella and the hyoid apparatus. These 

 may conveniently be considered together, as the 

 columella is, according to most authorities, the 

 uppermost part of the hyoid arch, just as the 

 quadrate is of the mandibular. 



i. The columella is a minute and slender rod of 

 bone, the proximal end of which is expanded 

 into an oval plate, fitted into the fenestra 

 ovalis of the tympanic cavity ; while the 

 outer or distal end, which is cartilaginous and 

 divided into three diverging arms, is attached 

 to the tympanic membrane. It serves to con- 

 vey the sound- vibrations from the tympanic 

 membrane to the membrane closing the 

 fenestra ovalis, and so to the internal ear. 



Owing to its small size and slight attach- 

 ment, the columella is often lost in macerated 

 skulls : it may, however, sometimes be found 

 projecting from the fenestra ovalis. 



ii. The hyoid apparatus is a bony framework, lying 

 in the floor of the mouth, and supporting the 

 tongue. It consists of a median jointed rod 

 of bone and cartilage, formed of glosso-hyal, 

 basi-hyal, and basi-branchial ; to the sides of 

 which are attached in front the short cerato- 

 hyals, and further back, the elongated and 

 jointed thyro-hyals, the ventral portions of 

 the first branchial arches. 



