Aproximately 1 mm. wide, which marks the transition between the cornea on the one hand, and the conjunctiva, the episcleral tissue and sclera on the other. It appears as a grey, semi-transparent area with a fairly well defined corneal edge and merging inconspicuously into the sclera. In shape it resembles two half-moons meeting at the horizontal meridian with the broadest parts in the vertical meridian where on occasion it may be 2-5 mm. in extent. The appearance of the surface is seldom uniform, but is generally broken by numerous white digitations, 1-5 to 2 mm. apart, which run radially, like the ribs of sand on the seashore, from the sclera to lose themselves in the clear cornea.