Carol,
The Hendler book might be the best for the SE as far as identifying your
heart urchin. The Treatise on Invertebrate Paleontology has a volume on
echinoids as well, which features many modern genera. If you have a
picture of this I could also help you - and if I can't, Rich Mooi at the
California Academy of Sciences, who works on echinoids could.
 
If you have a scanner, you could make a jpg of this simply by laying it
on top and scanning. You might want to see what the results of this
process looks like by visiting my echinoid page at
http://kendaco.telebyte.com/cburns/echinoid.html
 
Regards,
Casey Burns
Casey Burns - Wind Instrument Maker and Occasional Paleontologist
9962 Shorty Campbell Road  Kingston WA 98346
(360) 297-4020
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http://kendaco.telebyte.com/cburns