Such visually dependent behavior patterns are
consistent with the retina of P. regius. Even in the absence of
a specialized region of high cone density (Walls, 1942), the
rod:cone ratio of approximately 10:1 found in P. regius reflects
a cone density of approximately 45 000 cellsmm-2. This is less
than the cone packing density in the central retina of the owl
monkey (78 000 conesmm-2; Ogden, 1975), but substantially
greater than the cone density in the area centralis of either the
North American opossum (8000 conesmm-2; Kolb and Wang,
1985) or the cat (27 000 conesmm-2; Steinberg et al., 1973).
Strictly on the basis of cone packing density, it would not be
unreasonable to conclude that the photopic visual resolution of
P. regius should be better than that of the cat.