... or maybe a Watermelon Spider* since the abdomen looks like a watermelon. Either way, he was pretty cool. We found him meditating in the Catican. I left the photo fairly big and he's worth a click to see him in full detail. The eye structure in particular was fascinating for me.
* - In reality, it was a Green Lynx Spider, Peucetia viridians. Identification thanks to the Spider Identification Guide. You can read lots more about him here.