Eight-legged hobbit?

Hermit crabs live in borrowed snail shells. "True" crabs hide themselves under rocks, or bury themselves up to the eyestalks in the sand. But one of my little crabs has taken a hint from the hermits.

I provided an assortment of shells for the hermits; whatever I could find or had collected from other sources. Some are from local beaches, some from Mexico and Central America, a few from unknown shores, shells I picked up in garage sale lots.  But hermits have their likes and dislikes; some will accept even non-shell outfits, made of glass, broken bottle caps, or even Lego (look!) but many have very specific tastes. Mine, hermits from Boundary Bay, will only wear discarded shells from local species of marine snails: whelk, mud snails, or periwinkles. Everything else is invisible to them, so far.

One of the smaller shore crabs discovered a broken shell ignored by the hermits, and moved in.

Hobbit house* shell, from down south, is about 1 1/2 inches across.

The shell makes a great shelter; front and back doors, complete privacy, no maintenance. The crab stays inside most of the time, even when I pick up the shell as I clean the aquarium, or when larger crabs push it around. He comes out when I provide crab treats, only to grab his share and retreat to eat it in his own space.

I was surprised, a couple of days ago, to see him out of the shell, digging busily deep in the sand a couple of inches away. I watched. After a minute, he surfaced carrying a large white stone, which he carried over to his home shell, and deposited in the doorway. There were already several others there, in both openings.

Front door, back door, with privacy screens. He's well hidden inside.

The stones fell out when I tidied the aquarium yesterday, but he's since added a new sandy floor inside and three fresh stones at the doors.

*It had a perfectly round door like a porthole, painted green, with a shiny yellow brass knob in the exact middle. The door opened on to a tube-shaped hall like a tunnel: a very comfortable tunnel without smoke, with panelled walls, and floors tiled and carpeted, provided with polished chairs, and lots and lots of pegs for hats and coats ... J.R.R. Tolkien, The Hobbit