210 CLASS XV. 



composed of several separate bony pieces, of which one serves for 

 articulation with the lower jaw (the quadrate hone). In the hatra- 

 chians the jugal bone also contributes to form the articular tubercle, 

 which is received by the articular surface of the lower jaw. The 

 cranium is always small in comparison with the rest of the bony 

 head, so that in some (the frog, ex. gr. and the chameleon) the 

 orbital cavity is larger than the space in which the brain is 

 contained. 



In forming the upper jaw the intermaxillary bones are of much 

 less importance than in the class of fishes; here they constitute 

 only the middle part of the upper margin of the oral aperture. In 

 the serpents and in most of the saurians they coalesce to form an 

 unpaired bone. The under jaw constantly consists of a greater 

 number of pieces than in mammals. The articular piece, which 

 is in connexion with the quadrate bone, always continues distinct 

 from the anterior part, in which the teeth are fixed. The two 

 halves of the lower jaw are united with one another in the middle 

 without suture In the chelonlans, but continue distinct from each 

 other In the rest. 



Most reptiles have teeth, which, however, in all the chelonlans 

 and in Pi/pa amongst the batrachians are wanting. In the first of 

 these the two jaws are usually covered with a fibrous horny tissue. 

 The teeth serve, not so much for dividing or chewing, as for hold- 

 ing fast the food ; their form too does not differ, as In the mammals 

 and many fishes, in the different parts of the oral cavity, and the 

 distinction as incisive, cuspidate and molar teeth, falls to the ground. 

 In most saurians the teeth are only in a single row In botli jaws ; 

 in some there are also teeth In the palate. In the serpents there is 

 a row of teeth on each side in the palate, and usually a row in the 

 two jaws. On the poison-teeth of serpents we shall treat after- 

 wards in the systematic arrangement of this class. In the batra- 

 chians teeth are usually found In the palate (in the vomer), and also 

 a row of small, thin, conical or card-shaped teeth in the upper jaw, 

 which however are wanting in most toads. The salamanders have 

 such teeth in both jaws. 



The tongue sometimes serves for the capture of food. The 

 batrachians catch small animals with it; here the tongue is at- 

 tached forwards to the margin of the lower jaw and with the free 

 part thrown back ; this part can reverse itself and be projected 



