THE OPHIDIA. 207 



The latter is long and stout, and, as usual, is united, be- 

 nind, with the distal end of the quadrate bone. In front of, 

 and internal to, its union with the transverse it is prolonged 

 forward, and becomes united, by a movable joint, with the 

 short palatine bone, which is flattened from side to side, 

 and lies on the outer side of the posterior nasal aperture. Its 

 anterior end is connected only by fibrous tissue with the base 

 of the skull. The inferior edge of the palatine bears a few 

 small teeth, and other sharp, recurved, solid teeth are attached 

 to the under-surface of the anterior moiety of the pterygoid. 



When the mouth is shut, the axis of the quadrate bone 

 is inclined downward and backward. The pterygoid, thrown 

 as far back as it can go, straightens the pterygo-palatine joint, 

 and causes the axes of the palatine and pterygoid bones to 

 coincide. The transverse, also carried back by the pterygoid, 

 similarly pulls the posterior part of the maxilla, and causes 

 its proper palatine face, to which the great channelled poison- 

 fangs are attached, to look backward. Hence these fangs lie 

 along the roof of the mouth, concealed between folds of the 

 mucous membrane. But, when the animal opens its mouth 

 for the purpose of striking its prey, the digastric muscle, pull- 

 ing up the angle of the mandible, at the same time thrusts 

 the distal end of the quadrate bone forward. This necessitates 

 the pushing forward of the pterygoid, the result of which is 

 twofold ; firstly, the bending of the pterygo-palatine joint ; 

 secondly, the partial rotation of the maxillary upon its lachry- 

 mal joint, the hinder edge of the maxillary being thrust down- 

 ward and forward. In virtue of this rotation of the maxillary, 

 through about a quarter of a circle, the dentigerous Tace of the 

 maxilla looks downward, and even a little forward, instead of 

 backward, and the fangs are erected into a vertical position. 

 The snake " strikes : " by the simultaneous contraction of the 

 crotaphite muscle, part of which extends over the poisou- 

 gland, the poison is injected into the wound through the canal 

 of the fang; and, this being withdrawn, the mouth is shut, all 

 the previous movements are reversed, and the parts return to 

 their first position. 



No Ophidian possesses any trace of anterior extremities, 

 but the TyphlopidcB, the Pythons, Boas, and Tortrices, have 

 rudiments of a pelvis, and the latter Snakes even possess very 

 short representatives of hind-limbs terminated by claws. 



The teeth of the Ophidia are short and conical, and be- 

 come anchylosed to the bones hy which they are supported. 



