120 



near the surface, we find merely a feeble annular disk ; while 

 the other birds of the group have the ring very strong and 

 convex : the Gannet, which takes its prey by descending per- 

 pendicularly from a considerable height, with great force into 

 the sea, has the individual bones stronger than any other bird I 

 have met with : — the true divers (which dive from the surface 

 to a considerable depth after their prey) have their ring very 

 strong and convex, though the individual bones are much 

 weaker than in the Gannet. The Guillemot, Razor-bill and 

 Sea Parrot, also have the ring very convex, especially the latter. 

 Here are ten specimens of Passerine birds : two have thirteen 

 bones ; five have fourteen ; one fifteen ; one uncertain ; and one 

 (the Podargus Humeralis) difiers from all other instances I 

 have met with ; the bony ring being composed of one single 

 bone, instead of a series of plates. The European Night Jar 

 has a very weak ring without any convexity ; while its Austra- 

 lian congener has the ring of considerable size ; though the bone 

 itself is of a soft and porous texture like the Owls. The Swift 

 has the ring larger, stronger and much more convex than any 

 other bird at all approaching its own size. The Kingfisher's is 

 also large for the size of the bird ; and the bones of the Hum- 

 ming-bird are also strong. 



Of E-eptiles, Cuvier says, (Comp. Anatom. translation, page 

 396,) " There are similar laminae in the sclerotic of the 

 Chameleon and several other Lizards ; but they do not form 

 the anterior disk of the eye ; but merely surround the lateral 

 part." Here are bones of two species of Turtle and three 

 species of Lizards ; Serpents and Frogs appear destitute of 

 them. The bones of the Turtle are less symmetrical than those 

 of birds or Lizards, and form a nearly flat disk, having but little 

 convexity. 



Out of three species of Lizard, which are all I have examined, 

 and of which the Chameleon is one, in two cases the ring, in 

 opposition to the statement of Cuvier, does form the anterior 

 disk of the eye, and that as completely as in any class of birds : 



