It's a Bob Marshall Circle Y Treeless Saddle. I've seen these on trail rides before and they look like they'd be really comfortable for both horse and rider. You can actually bend the saddle in half and make the cantle touch the pommel. I found this one on e-bay. The current bid is $768, which ain't bad for one of these. I think they sell for over $1000 normally.
I have seen them at the tack shop, but I don't know anyone who actually owns one. They seem interesting, and more comfortable than two bars, even well padded bars. They seem like they'd be good for a tough-to-fit horse, and would be close contact too.
I wonder if they are secure enough... My instinct looking at them was that they were sortof like a bareback pad with cantles and stirrups... I wonder if they would stay in place in a slippy situation without the tree... kindof like the risk with bareback pads that have stirrups.
I have no personal experience with one of those, but when they first came out, alot of the barrel racing people we knew tried them. They didn't like them and most of them went back to a regular saddle. If I understood them correctly their complaint about them was they did not hold their shape good and so would cause soreness in places on the horse. Like I said that is hear say so take it for what it is worth.
Becky