48 



THE SKELETON OF THE FROG 



part of its length : near its hinder end it is pro- 

 duced upwards into the coronary process. 



ii. The dentary is a flat bone covering the outer sur- 

 face of the distal half of Meek el's cartilage, as far 

 forward as the mentomeckelian bone. 



iii. The mentomeckelian is a small ossification in 

 Meckel's cartilage at the symphysis, i.e., the 

 union of the arches of the two sides at the chin. 



x K M 



o N 



AS 



I / 



H V 



FIG. to. A transverse section across the posterior part of the frog's 

 head, to show the position and relations of the auditory organs, 

 Eustachian tubes, and hyoid apparatus. On the right side the section 

 passes through the lympanic cavity and the columella ; on the left side 

 through the anterior cornu of the hyoid. The cartilage is dotted, and 

 the bones, except the columella, are represented black. 



A, parasphenoid ; AS, angulosplenial ; B, buccal cavity ; C, colu- 

 mella ; D, tympanic membrane ; E, ffufita^' 3 " '"Vf ; F, anterior 

 cornu of the hyoid; FP, frontoparietal ; G.^glojlis; H, arytenoid 



^ 



cartilage ; I, posterior cornu of hyoid ; K, auditory nerve ; L, vesti- 

 bule ; M, anterioi vertical semicircular canal ; N, horizontal semi- 

 circular canal ; O, pro-otic ; P, pterygoid ; Q, quadrate cartilage ; 

 R, " quadratojngal " ; S, squamosal ; T, annulus tympanicus ; V, yocal 

 cord ; X, mid-brain. 



4. The Hyoid Apparatus (Fig. 9). This consists of the 

 hyoidean arch and the remains of the branchial arches 

 of the two sides, together with a median ventral 

 plate, the body of the hyoid, which unites their 

 lower ends together, and lies in the floor of the mouth. 

 The hyoid apparatus consists almost entirely of 

 cartilage. 



