. Carnegie Institution of Washington publication. 56 BLIND VERTEBRATES AND THEIR EYES. THE EYES OF TYPHLOPS LUM BRICALIS. The eye shows through the large ocular scale, which entirely covers it. It appears as a black spot surrounded by an unpigmented circle. The preocular, also a large scale, overlaps the ocular and reaches just to the edge of the eye (figs. 20 a, b). Compared with one of the garter ^ as pas. os. snakes and in proportion to the size 11S ..-isJrw&-j °f trie head, the eye of Typhlops lum- . /c5(*/*rP bricalis is situated farther from the ra"vx)\^7 surface and occupi
. Carnegie Institution of Washington publication. 56 BLIND VERTEBRATES AND THEIR EYES. THE EYES OF TYPHLOPS LUM BRICALIS. The eye shows through the large ocular scale, which entirely covers it. It appears as a black spot surrounded by an unpigmented circle. The preocular, also a large scale, overlaps the ocular and reaches just to the edge of the eye (figs. 20 a, b). Compared with one of the garter ^ as pas. os. snakes and in proportion to the size 11S ..-isJrw&-j °f trie head, the eye of Typhlops lum- . /c5(*/*rP bricalis is situated farther from the ra"vx)\^7 surface and occupies far less space, while Harder's gland, associated with the eye in both, is relatively much larger in Typhlops. In a specimen of. FIG. 20. W Dorsal View of Head of Typhlops, 21 cm. long TvpklohS 1 lllllbric(llis 21 CITl. in length, (6) Lateral View of Head of same Specimen. ,~ the eye measured mm. in width, and mm. in depth. The greatest width of the gland of the same was mm. and the length was mm. The gland completely surrounds the eye up to the edges of the conjunctival sac (plate 4, figs. A, B). In proportion to the size of the eyes, the gland of the garter snake is much smaller than that of Typhlops liimbricalis, but compared with Rhincnra floridana the gland of Typhlops litinhricalis is but little more than half as large. The eye is covered by layers of epidermis and dermis that differ from these same layers on neighboring parts by being thinner, more compact, and free from pigment and glands. The ocular scale, however, which covers the eye region, does not differ in thickness from the other scales of the head (plate 4, fig. A). A conjunctival sac is present with a diameter at least as great as the greatest width of the eye bulb. The conjunctiva, which forms this sac, is very thin over the cornea and next to the brille, where it measures mm. At the edge of the sac it is differentiated into glands, the fornix conjunctiva, and measures m
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