Luminosity class IV is the last in which any appreciable spiral pattern is seen, albeit often only with some imagination. Galaxies of this class are usually no longer typed as Sc, but rather Sd or Sm.
The spiral pattern is most easily traced in NGC 7793, which is the brightest of the six at MBT0, i = - 18m.5. (This galaxy could perhaps be classed as SdIII-IV by comparison with the last panel, though we have not done so.) A single spiral plume, highly resolved into stars, is seen on the NW side of NGC 5585 (a companion to M101). A few "non-random" features in NGC 1156 suggest a spiral pattern similar to the imaginative case of the LMC. The pattern is not quite so subtle in NGC 5204 (another companion to M101; see Sandage and Tammann 1974c, table 3), and hence the galaxy is classed Sd.
Any spiral pattern in NGC 3109 and NGC 1569 (which are nearly edge-on) remains suggestive rather than visible. These systems are classed as SIV rather than SIV-V because of their high surface brightness.
NGC 7793 C100-510-S Sd(s)IV -18m.85S 220 km/s | 
NGC 5585 P200-76-B Sd(s)IV -18-46M 304 km/s |
NGC 1156 P200-1078-S SmIV -18m.32 373 km/s | 
NGC 5204 P200-18-H SdIV -18m.11 201 km/s |
NGC 3109 C100-155-S SmIV -17m.28 403 km/s | 
NGC 1569 P200-147-H SmIV -16m.22 -83 km/s |