Is this bear's head fungus?
I don't think this is bear's head tooth fungus, in large part because it is growing on the grass, not on wood.This look like a Fuligo species of Myxomycete, a slime mold. It won't hurt the plants, but it's best not to let the dog eat any fungi. Slime molds are edible, but without a definite identification (a sample has to be confirmed by a mycologist), you should not ever eat fungi or let animals eat them. You can rake it or spray it with a hose and it should wash away. Or you can let it be - it will change color and even seem to move a bit over the next few days, then when conditions dry out, it will also dry up and sort of disappear, leaving behind a lot of spores that will wait for the right conditions. Learn more here about a similar slime mold: http://plantclinic.cornell.edu/factsheets/slimemolds.pdf