Leo,
The bulge looks normal on the image you have displayed that emphasizes this feature of NGC7331 ; the bulge is observed to extend far above the plane of this galaxy, on both sides, as one would expect for a three-dimensional structure that is spheroidal.
But appearances can be deceptive...... because we get only a two-dimensional image in the telescope, and it has turned out that it is actually a difficult (non-trivial) task to derive the actual three-dimensional structures in galaxies from their two-dimensional images.
When this image is displayed at high brightness and contrast, the outline of this galaxy does display a high degree of symmetry and regularity.
Your other image Clearly shows a discrete and well-defined inner Ring or Disk structure within NGC 7331, which is also quite obvious at several different wavelengths:
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Nearly all of the prominent galaxies in the NGC 7331 field are at a much higher redshift than the big spiral; so they are actually far in the background. Oddly, the exception to this rule is actually a member of Stephan's Quintet : NGC 7320
(I am excluding from consideration, here, several candidate dwarf spheroidal companions of NGC 7331)
The recession velocity of NGC 7320 is closely similar to that of NGC 7331, so the most straightforward interpretation of this is that NGC 7320 is at a similar distance to NGC 7331 (despite all the "conspiracy theories" about this on the internet! )
Furthermore, NGC 7320 has an optically luminous streamer or tail that points towards NGC 7331, and this does provide some evidence for an interaction between these two galaxies.
Added information, in a later edit:
Halton Arp presented an image processing analysis of photographic plates of this field in (1976), Astrophysical Journal, Volume 210, page 58.
As is usual for old papers, the scan of the paper that can be found at //adsabs.harvard.edu is really ratty, so a more useful thing to do would be to access the paper (physical) version of this article.
It is obviously time for me to catch up on the literature about N7331!
