42 INTRODUCTION 



pterygoid are elongate and parallel to the axis 

 of the skull, the latter diverging behind and ex- 

 tending to the quadrate or to the articular extremity 

 of the mandible ; the pterygoid is connected with 

 the maxillary by the ectopterygoid or transverse 

 bone, which may be very elongate, and the maxillary 

 often emits a process towards the palatine, the latter 

 bone being usually produced inwards and upwards 

 towards the anterior extremity of the basisphenoid. 

 The quadrate is usually large and elongate, and 

 attached to the cranium through the supratemporal 

 (often regarded as the squamosal). In rare cases 

 (Miodon, Polemon) the transverse bone is forked, and 

 articulates with two branches of the maxilla. The 

 quadrate and the maxillary and palatopterygoid 

 arches are more or less movable to allow for the 

 distension required by the passage of prey, often 

 much exceeding the calibre of the mouth. For the 

 same reason, the rami of the lower jaw, which con- 

 sist of dentary, splenial, angular, and articular 

 elements, with the addition of a coronoid in the 

 Boidae and a few other small families, are connected 

 at the symphysis by a very extensible elastic ligament. 



The hyoid apparatus is reduced to a pair of cartila- 

 ginous filaments situated below the trachea, and 

 united in front. 



There are various modifications according to the 

 genera. A large vacuity may be present between the 

 frontal bones and the basisphenoid (Psanwiophis, 



