In the so-called "ideal" female figure (the hourglass), the waist is about 70% as wide as the hips. That translates to about a ten inch difference, which is pretty much what you have. Your bust and hip measurements are pretty close. So, yes, I would agree (in the absence of a photo) that you are probably a slim hourglass.
The main reason a photograph makes a difference is that it's not just the three numbers -- bust, waist, hips -- that matter here. For example, I don't know how broad or angular your shoulders are. That can matter more than the size of your breasts in terms of determining body shape. Also, I don't know how long or short your legs are, or how long- or short-waisted you are. If you're short-waisted, you're likely to look a bit more rectangular than hourglassy, given your measurements.
Imogen Lamport explains it well. Here's the link to her first blog entry on "body shapes explained":
http://www.insideoutstyleblog......pes-8.html
Check the right-hand sidebar for the other body shapes. Hope that helps!
