Sketch of the disk for an epoch in B275 and B243. The positive trend of the V/R ratio and the peak-to-peak velocity might be explained by a spiral arm in the disks of B275 and B243. We show two examples of face-on inner gaseous disks with a spiral arm and line-forming regions in the disk of the higher- and lower-order HI lines, where the line region of the latter extends to the surface of the star. Typical double-peaked emission lines are shown for these HI lines. The panels that show the V/R ratio on the y-axis and the peak-to-peak velocity on the x-axis mimic the epochs shown in Fig. 9.