12 Mr. Bell on the Structure 



This genus comprehends such of the Linnean Lacertce^ as have 

 long, unequal toes, the penultimate phalanges of which are di- 

 lated in such a manner, as to allow of their running with facility 

 upon perpendicular surfaces, by means of a mechanism similar to 

 that which Sir Everard Home has demonstrated as belonging to 

 the foot of the Gecko, and of the Window Fly : namely by the 

 production of a vacuum beneath the foot.* But the peculiarity 

 which forms the subject of this paper consists in the skin of the 

 throat being more or less pendulous, and capable of great expan- 

 sion, so as to form at the will of the animal, an enormous protube- 

 rance, reaching in many species from the anterior part of the 

 lower jaw to nearly the middle of the belly. 



This dilatation takes place when the animal is excited by anger 

 or desire. It has been taken for granted by naturalists, judging 

 from mere external appearances, that this remarkable enlargement 

 is produced by inflation^ and hence various authors who have taken 

 this circumstance as a character of the genus, have adopted terms 

 expressive of such an opinion. + Thus Cuvier says, " la plupart por- 

 tent un fanon, ou un Goitre sous la gorge, qu'ils enflent." Mer-. 

 rem also gives as one of his characters, " Corpus iiiflabile,^'' ob- 

 serving, ** Sie Jconnen den Rumpf aufblasen.'''' " They have the. 

 power of inflating the belly." Having lately received numerous 

 specimens of this genus from Madeira, and from the West Indies, 

 I have had an opportunity of making repeated dissections oT this 

 part in several species, and of ascertaining the precise mode in 

 which this presumed inflation is produced. 



The frame work of this structure consists of a remarkable de- 

 velopement of the os hy aides ^ or bone of the tongue. This bone 



* A similar structure has been demonstrated in the flippers of the Walrus 

 by the same eminent comparative anatomist; of which an account is given in 

 the present Number of this Journal. 



+ It is the more remarkable that this error should have obtained, as it is 

 Well known that the protuberance beneath the throat in the different species of 

 Iguana, is supported by a cartilaginous process of the os hyoides; and this is 

 one only of many interesting affinities between these two groups^ which I hope 

 to take an early opportunity of illustrating. 



