Spine chain stitch
This stitch is similar to Mountmellick stitch as both are chain stitches with protruding spines. In this version the spines protrude from alternate sides, rather than always extending from the same side.
Bring the needle and thread to the surface, then take the needle back down through the same hole leaving a loop on the surface.
Bring the needle up again within the loop, the distance will determine the size of your loop.
Holding the working thread on the underside pull the thread against the needle to tighten the loop to create your first chain stitch.
Bring the thread up to the surface and create an angled straight stitch off to one side.
Repeat steps 1 - 3 ensuring to bring the needle up and down within the base of the first chain.
Stitch another angled leg out to the side, this time on the opposite side from the last.
Structure of stitch
Mary Thomas, Jan Eaton, Mary Thomas’s Dictionary of Embroidery Stitches (Revised Edition) (1989) , p.38