I agree with NanoCrazed above, that it's
Heteractis magnifica, also known as a ritteri anemone.
Its short tentacle shape as shown in the picture is a possible sign of stress or it being very young. For me, the blunt tentacles and the striated base as seen in the 2nd and 3rd shown is what makes me think it's H. magnifica. Way too much information here: <
http://eol.org/pages/420986/details>
It will likely color up given the proper lighting and water quality, and the tentacles will become longer. However, brown is good! In this new world of wildly-colored designer zoas and SPS, there seems to be a denial of the fact that many healthy photosynthetic cnidarians are brown.
They live for perhaps over a hundred years in the wild, but survival in captivity is not usually good. I had one for almost three years. My suggestion would be to make it the center of a pristine specimen tank, with a good biofilter of live rock, with carefully shielded overflows and no exposed powerhead intakes, as they can wander. Many species of clownfish are known to associate with this species, including ocellaris and percula, skunks, and clarkii, among many others (see link above as well).
I could be wrong! Keep us posted on this beautiful creature's progress!