34 ON THE PHYSIOGNOMY OF SERPENTS. 



anteriorly with the palatals, form with the latter two 

 branches, most frequently in the form of an S, extending 

 almost the w^liole length of the cranium. Their anterior 

 extremity is either free or united to the vomer by ligaments, 

 the posterior end is attached to the internal edge of the 

 tympanite near its base. These bony slips, except in the 

 Oligodon alone, are armed with teeth. Besides its union 

 with the external pterygoid, the internal pterygoid is con- 

 nected in many non-venomous serpents with the sphenoid. 

 The same is the case with the palatals, which in all that 

 tribe, and in all the true venomous snakes, are attached, 

 by means of a small apophysis, to the base of the cranium. 

 It remains that I describe the loiuer jaw. Everybody 

 knows that its two branches are joined by a ligament at 

 their anterior extremity, instead of being ankylosed. Each 

 branch is composed of two principal parts, the dentiferous 

 and the articular portions, of which the sutures are covered, 

 on the internal face, by three little supernumerary bones ; 

 the superior piece has been compared to the coronoid pro- 

 cess in the skeleton of the mammifera ; but in many Ophi- 

 dians, especially in the non-venomous serpents, the portion 

 of which we now speak is almost reduced to nothing, and 

 is placed under the dentiferous part ; whilst the true coro- 

 noid process is well developed, and occupies the posterior 

 part of the articular portion near its junction with the 

 tympanites. The dentiferous part alone supporting the 

 teeth is always bristled with them throughout its length ; 

 it varies considerably in the different species, has acquired 

 the gi*eatest development in the Boa, and is least in the 

 venomous snakes. It is superfluous to remark, that the 

 development of the two principal portions of the lower jaw 

 have an inverse ratio to each other, and that the extent of 

 the whole of that jaw naturally augments with the size of 

 its suspensory bones. These supporting bones occur as a 

 pair on each side : 1st, The mastoid bone, attached to the 

 cranium above the pars petrosa ; and, 2d, The drumsticks 

 or ti/mpanitic bones,* attached to the mastoids by ligaments, 



[* The bones are denominated in French les Caisses, or les Tymjyaniques. 

 They have no analogy in the skeletons of mammifera, unless we consider 

 them representing the upright angular portion of the lower jaw.] 



