228 



ANAT01MY OF VERTEBRATES. 



process of the mandible. From fascia attached to the neural 

 spines of some of the anterior vertebrae there extends a flattened 

 muscle, Heuro-inandibidaris, fig. 145, t, which unites with a smaller 

 strip from fascia connected with the ribs of those vertebrae, 

 costo-mandibularis, figs. 145, 147, ?/, to be inserted into the lower 

 border of the mandible. These muscles depress and retract the 

 lower jaw. 



A powerful muscle, ectopteryyoideus, fig. 146, 7i, which in its 

 mandibular relations resembles the external pterygoid, advances 



146 



Muscles of the pterygo-palatine apparatus of the Crotalns. cxcu. 



forward to the fore part of the ectopterygoid, and to the back part 

 of the maxillary in Python. In Crotalus it expands into a fascia, 

 spread over the pouch lodging the venom-fangs, preserving a 

 tract of tendinous strength for insertion into the lower part of the 

 hinder process of the maxillary. It cooperates with the erector 

 of the fang in fixing the moveable maxilla during the blow, and 

 retracts the fang on the relaxation of the erector. When its fore 

 part is the fixed point, the ectopterygoideus spreading its man- 



