OF THE BONES OF THE HEAD. 33 



vestiges of these bones ; they disappear in the Tortrix and 

 the Elaps, while they are highly developed in the Boa, 

 in many Vipers, &c. ; but in the Acrochordus they extend 

 to the anterior frontals, and thus replace the supraorbitars, 

 another pair of supernumerary osseous pieces, peculiar to 

 the Pythons, and wedged between the frontals. 



All the other bones of the head belong more or less di- 

 rectly to the great apparatus destined for mastication, if 

 such a term may be employed in describing the animals of 

 which we now treat. This apparatus is naturally divided 

 into two parts : the first consists of the upper jaw and its 

 appendages ; the second is formed by the lower jaw, and 

 tlie pieces which suspend it from the cranium. It is first 

 necessary to describe the intermaxillary^ a little bone placed 

 transversely at the end of the snout, rarely armed with 

 teeth, the handle of which is lodged l^etween the nasals and 

 the vomer ; being in other points free, it follows the move- 

 ments of these bones. The maxillaries, equally free at 

 their anterior extremity, are united to the cranium, through 

 the medium of the anterior frontals ; their posterior extre- 

 mity is bound to the external pterygoids ; but it by no 

 means follows that their form and their mode of attach- 

 ment should ahvays be the same in the difii'erent genera of 

 Ophidians. In non- venomous serpents, this bone is pretty 

 long, horizontally placed, armed with a row of numerous 

 teeth, and always united by a bridge more or less wide to 

 the palatal bones, or even to the internal pterygoids. In 

 the poisonous snakes, on the contrary, it is reduced to a 

 very short piece, and always smaller according as the 

 serpent is more poisonous. We observe in the venom- 

 ous snakes, that this bone only supports the fangs, is arti- 

 culated only to the anterior frontals, and is free in all the 

 rest of its extent. It is evident, that the development of 

 the external pterygoids, real levers of the upper jaw, should 

 be in the inverse ratio to that of the maxillaries. This 

 piece, intermediate between the maxillaries and the internal 

 pterygoids, is always without teeth, and becomes more 

 slender as it increases in length ; it consequently shews 

 itself in the shape of a linear and very slender stylet in 

 venomous snakes. The internal pterygoids, which unite 



