Figure 14. The structure and placement of ossicular rings. Rings of bony plates surrounding the iris of the eye are present in most reptiles. On the left is a drawing of the arrangement of the plates, variously referred to as sclerotic or scleral ossicles, ossicular rings etc. from the eye of a tuatara. The eyeball is that of an albatross depicted from the side in order to show how the ossicles shape the junction between the cornea and the sclera. To the right and bottom are depictions of the skull of an eagle and a Lambeosaurus, respectively, showing the positioning of the ossicles within the orbit. The primary purpose of the ossicles appears to be to reinforce the corneal scleral junction. In birds, the ossicles allow the animals to adjust the shape of the cornea during accommodation. (Top 3 drawings adapted from Walls 1942; lambeosaur adapted from Colbert 1961).