SMBH mass–pitch angle relation for all available directly measured black hole masses (as in Figure  1) and for those masses estimated indirectly via σ in our preferred sample (see Table 1 and Section 2.1 for details). The fit to the SMBH mass–pitch angle relation for this extended data set is log ( M _BH/ M _☉) = (8.36 ± 0.15) − (0.076 ± 0.008) P with a χ ² = 10.43 and a scatter of 0.45 dex. This fit is consistent with that obtained from our sample of directly measured black hole masses (Figure  1) and is almost identical to the fit given in Seigar et al. (2008). The addition of σ-derived masses, several of which are at the low-mass end of our distribution, tends to confirm the validity of the complete sample fit shown in Figure  1 against the much shallower fit found for the maser-modeling-only data shown in Figure  2. Black ×'s represent data from stellar or gas dynamics (10 points), blue squares represent data from maser modeling (12 points), red triangles come from reverberation mapping data (12 points), and magenta octagons represent masses derived from the M–σ relation (20 points).