Correction

In the recently published article by Cameron et al. [Volume 64, Number 1, 2007, pages 19–48], the pages on which figures 2 and 8 should have appeared were inadvertantly switched. Figure 2 should have been on page 24, where figure 8 was misplaced. Figure 8 should have been on page 33 in place of figure 2. No other elements of the text were affected.