Does this help? I think I understand which part you are referring to, which would make it rotundum, but I'll leave it up to you if its clear enough in the photo.
The brown one was very small (from memory c5-7mm body length), and again the decision is yours as to whether it can be done or not. However, I can see similarities between this and Metellina segmentata, and it has indeed given me ideas for at least one of my remaining unidentified spiders. More on this later.