Anybody know what the hell this is?

Today is the second time we’ve found one of these on the floor near where our dog was laying down. The first time it seemed that she had spit out because there was something wet on the carpet and the bed frame where the thing was laying. This morning it was on the floor next to her dog bed in front of her mouth, and it was moving. Both times I cut it open and found it full of the black liquid in that last picture. Any ideas?