Found that pattern.
SOFT-SHELL CRAYFISH
ByWWRyan
HOOK: #4#8, 2XL.
THREAD: White, brown, or olive monocord.
KEEL: Two strips of lead wire.
UNDERBODY: Fox or rabbit fur mixed with Antron.
CARAPACE: Olive, sandy, gray, or brown bucktail.
CLAWS: Small bunches of fox or rabbit fur with guard hairs.
LEGS: Grouse breast feathers.
CEMENT: Dave's Flexament.
1. Secure two strips of lead on top of the hook shank for the keel (which will keep the hook upside down). Cement and wrap the hook with thread.
2. Flip the hook in the vise (so that it's upside down). Tie in buck tail strands by the tips at the bend of the hook. (Make sure they are long enough to be tied back over the hook with the butt ends extending past the eye.)
3. Dub the cephalothorax of the fly. Tie off, keeping a length of dubbed thread for later use.
4. Tie in fox fur for claws and wind on grouse hackle for legs
5. Wind reserve dubbing from the thorax, crisscrossing the claws and gathering the grouse fibers into bunches. Tie this section fat.
6. Pull the bucktail back over the fly tightly; keeping it spread over the top half of the thorax. Tie it down tightly just past the grouse-hackle legs, and cement the winding. Tie in a strand of monocord (I tie in two in case one breaks). Tie in the dubbed thread and wind it to form the abdomen. Pull the bucktail back and tie it off at the eye. Rib the body tightly with the monocord to create segments, and tie off. Cement the entire bucktail carapace.
7. To finish the fly, use your thumb and forefinger to create a fold in the bucktail over the eye. It should look like the lip on a diving plug, except that it's on top. After you've created a crease in the buck-tail, cement it thoroughly with Flexament. This reverse lip will cause the fly to hop off the bottom (and over obstructions) when it is retrieved. The curved lip also pushes a tiny pocket of water when you twitch the fly, as does the tail of a live crayfish when it scoots off. Finally (this procedure may be the most important), pick out fur to enhance the soft under-body.