THE TEETH. 323 



b. The teeth of the lower jaw. 



i. The incisors are two in number, and project for- 

 wards from the anterior end of the mandible. 

 They are similar to the large upper incisors, 

 but are less strongly curved and are not 

 grooved : the alveoli in which they are lodged 

 extend back in the jaw as far as the anterior 

 grinders. 



ii. The grinding teeth form a set of five on each 

 side, placed opposite those of the upper jaw, 

 and like these are divisible into two groups. 

 They differ from the upper grinders in being 

 curved so as to be convex instead of concave 

 outwards. 



a. The premolars are the two anterior grinders 

 on each side. They are somewhat similar 

 to the upper ones, but narrower from side 

 to side. The outer surface of the first, 

 which is the larger of the two, is marked 

 by two deep longitudinal grooves, and that 

 of the second by a single groove. The 

 inner surface of each is less deeply grooved 

 than the outer. 



/3. The molars are the three hinder grinders on 

 each side : they are similar to the second 

 premolars, but have no deciduous prede- 

 cessors : the hindmost one is smaller and 

 simpler than the other two. 



II. THE APPENDICULAR SKELETON. 



The appendicular skeleton comprises the bones of the two 

 pairs of limbs, and the girdles which support them. The 

 bones of the limbs are mostly elongated, and provided with 

 epiphyses at their ends. 



A. The Pectoral Girdle. 



This lies outside the ribs, and is attached to the axial 



