Vol. 188 No. 3, February 8, 2010. Pages 415–428.

The authors have requested the following corrections:

In the discussion of the polar coordinate system leading to Eq. (1), the azimuthal angle φ is ambiguously defined as “measured around the z-axis.” A more conventional precise definition is “measured around the z-axis starting from the x-axis.” With this standard definition, the expression for S in Eq. (1) should contain the factor sin2φ instead of cos2φ. (The factor cos2φ is correct only if φ is understood to be measured from the y-axis.) All of the geometrical models considered in the paper are azimuthally isotropic, so the starting axis for measuring φ makes no difference whatsoever in the subsequent analysis.

Also, in the equation for orientational distribution η(plane), shown before Eq. (5), the delta function factor δ(θ − π/2) is best written as δ(cosθ). This makes no difference for the particular case here, but a δ-function distribution at any general polar angle θo must be written as δ(cosθ − cosθo).

We thank Dr. Nancy L. Thompson for suggesting these changes.