Cones are found primarily in the center (or fovea) of the retina. The fovea on the retina; which yields higher visual acuity, is not well-developed. The retinal fovea takes slightly different forms in different types of animals. These cones are the 'midget' pathways that also underpin high acuity functions of the fovea. This differs from tarsiers, which lack a tapetum lucidum but possess a fovea. The maximum density of blue cones occurs in a ring about the fovea. Cones are mostly concentrated in and near the fovea. Cones in the central fovea express pigments that are sensitive to green and red light. With only a postorbital bar, lemurs have been unable to develop a fovea. Eagles have a second fovea and three eyelids (two of which are visible). Meridians correspond to sections of great circles passing through the centre of the fovea. This anatomy is responsible for the depression in the center of the fovea. The Latin word "fovea" means "pitfall". The fovea produces the most accurate information. The term fovea comes from the .