Truncated cone circumscribed about a sphere of radius R. The apparent angular radius of the truncated cone (or the sphere) as seen from the observer at O is θ_R. Redshifts z₁ and z₂, the lower and upper limits of the truncated cone, respectively, vary as the radius of the sphere at the central redshift z_cen varies. The thin slice at z_cen has a thickness of Δr = 7 h⁻¹ Mpc. We counted galaxies inside the truncated cone which is centered on every galaxy within the slice.