446 MANUAL OF ZOOLOGY sect. 



having teeth which are perforated for the ducts of poison- 

 glands. In the snakes (Fig. 267) teeth are rarely devel- 

 oped on the pre-maxillse, but are present on the maxillae, 

 palatines, pterygoids, and sometimes the transverse bones, 

 as well as the dentary of the mandible. They may be of 

 the same nature throughout, solid, elongated, sharp-pointed 

 teeth, which are usually strongly recurved, so that they have 

 the character of sharp hooks, their function being rather to 



Fig. 268. — Pectoral arch and sternum of a lizard (Lacerta agilis). cl, clavicle; 

 cor, coracoid; ep. cor, epicoracoid ; epist, episternum; glen, glenoid cavity for 

 head of humerus; pr. cor, pro-coracoid; r I — r. 4, first to fourth sternal ribs; 

 sc, scapula; st, sternum; supra, sc, supra-scapula. (After Hoffman.) 



hold the prey and prevent it slipping from the mouth while 

 being swallowed than to masticate it. Non-venomous snakes 

 possess teeth only of this character. In the venomous snakes, 

 more or fewer of the maxillary teeth assume the character 

 of poison-fangs. These are usually much larger than the 

 ordinary teeth, and either grooved or perforated by a canal 



