Excellent suggestion, but I would favor C. monticola . While generally this also fits the markings and location of C. transversoguttata, the absence of any sign of a humeral spot, combined with the heavy spots present, suggests to me that this is probably C. monticola (see also MCZ type). To be postive we should have a image of the ventral pronotum spot (and given your location, a head shot, just to ensure this isn't some variation of C. trifasciata subversa). But I'd suggest this can be moved to C. monticola with some confidence.

Gordon states C. monticola is a widespread speces (coast to coast), but is less frequently encountered than some others.

I appear to have to constantly relearn the lesson to take more shots. Maybe I'll see this species again and get a second chance.

I had to take a shot :) One day I'll have it down and be as good as you. Any suggested studies beside Gordan '85?

I don't really know any of these. I just read and study and re-read the book, then make the best case I can put together. Oh, that we had references like these for many more families. It's really an exception to most other insect reasources in that it's complete for area of interest (for the entire NAm and nothing but NAm), it's complete down to species (most go to genus at best), and it's readable by a non-expert. It's just not very AVAILABLE! Although if you don't have access to one I'd encourage you to keep searching for a copy. Perhaps your library can arrange to borrow one on inter-library loan and you could copy a couple of genera that interest you most. And I believe Denis added a method to access it on-line (see it's book citation page here in the Guide), if you have connections (mostly through a Univ lib or professional subscription)

Update - Hey! I see that you yourself found a more accessable on-line copy. Great job! (and now I don't have to fear fire, flood, and lost luggage! Rather, I'll get to see others enjoy the benefits of having all the right information needed to ID the ladybirds!)