158 ANIMAL BIOLOGY. [Part I. 



ginous suspensorium directed outwards, and so far backwards 

 that the articular surface is nearly on a level with the occipital 

 condyles. At the end of this suspensorium a quadrate ossifica- 

 tion is formed in the cartilage, and constitutes the posterior end 

 of the quadrato-jugal. Dorsally the cartilage is strengthened 

 and supported by the overlying handle of the squamosal. 

 Ventrally it is supported by the outer limb of the pterygoid, 

 the inner limb of which is moveably articulated to the para- 

 sphenoid, while the anterior limb runs alongside the maxilla. 



By means of this suspensorial apparatus the articulation of 

 the lower jaw, which differs from that of both rabbit and fowl, 

 is carried away from the brain-case outwards and backwards. 

 This gives the long broad gape of the adult frog. In young 

 frogs this swinging outwards and backwards of the suspensorium 

 is not carried nearly so far. In a minute frog, the tail of which 

 has only just been absorbed, the suspensorium is directed as 

 much forwards as, in the adult frog, it is directed backwards, so 

 that the gape is very much shorter. 



The lower jaw itself contains a rod of cartilage (Meckel's). 

 There are three ossifications in each ramus : (1) a small mento- 

 meckelian (m. mk.) anteriorly; (2) a dentary (d.) forming the 

 upper part of the anterior half of the remainder of the jaw; 

 and (3) an angulo-splenial, by some regarded as articulare, 

 ensheathing the rest of Meckel's cartilage. 



(7.) The Hyoid. The form of the hyo-branchial plate (b. h.), 

 with its posterior and anterior cornua (p. c. 9 a. c.), will be 'seen 

 by reference to Fig. 50, D. The posterior cornua pass one on 

 each side of the glottis. The anterior cornua are confluent 

 with the periotic capsule close to the fenestra ovalis. 



The Chondrocranium. The form of the chondrocranium will 

 be made out by reference to Fig. 50, A. In it we find : (1) A 

 cartilaginous brain-case interrupted by an anterior and two 

 posterior fontanelles (a. /., p. /.), which lie beneath the parieto- 

 frontal bones. The cartilage is to a large extent invaded by 

 bone forming posteriorly the ex-occipitals, and anteriorly the 

 sphenethmoid (s. e.). (2) The auditory capsules (au. c,), largely 

 invaded by the prootics and, according to some observers, the 



