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Plate 3: The Eye of Birds and of the Eel

Fig. 1, 2. The flexible rim, or hoop, of the eye of birds, consisting of bony plates, which occupy the front of the sclerotic; lying close together and overlapping each other. These bony plates in general form a slightly convex ring, Fig. 1, but in the accipitres they form a concave ring, as in Fig. 2, the bony rim of a hawk.

Fig. 3, 4, 6. Exhibit the marsupium; it arises from the back of the eye, proceeding apparently through a slit in the retina; it passes obliquely into the vitreous humour, and terminates in that part, as in the eagle. Fig. 3, a section of the eye of the falco chrysaetos. In some species it reaches the lens, and is attached to it as in Fig. 4, 6. In the plate the marsupium is marked with a *.

Fig. 5. The head of an eel; the skin is represented turned back; and as the transparent, horny covering of the eye, a, a, is a cuticular covering, it is separated with it. Other fish have a similar, insensible, dense, and thick adnata, which is designed to protect the eye; and it seems especially necessary, as fish have no eyelids.