Body with a central disc of up to 12-13 mm in diameter and 5 thin and flexible arms of 15 times that length; coloured brownish or greyish.
Disc covered with scales on both sides. The primary plates are inconspicuous. The radial shields are small, smooth and separated (A. brachiata disc).
In the proximal part of the arms are 8-10 (sometimes 12-13) pairs of short arm spines per segment and the tube foot pores are covered by 2 tentacle scales. In the distal half of the arms there are no tentacle scales. The dorsal arm plates are very short, the ventral arm plates are short and broad, nearly rectangular (A. brachiata arm).
The mouth shields are spearhead- shaped, with a conspicuous outer lobe. There are paired infradental papillae on top of the jaws and one broad, scale-like and somewhat folded outer mouth papilla on each side of the jaws, not contiguous with the infradental papillae. Two pairs of tube-feet within the mouth (A. brachiata mouth).
This species lives buried in sandy bottoms, with the point of the arms just protruding above the surface.