(Delle Chiaje, 1829)
Body with a central disc of up to 5 mm in diameter and five radiating arms of ca. four times that length; coloured greyish or bluish-white.
Disc covered on both sides by rather small scales, among which the primary plates are scarcely distinguishable. Near the edge there is usual a sharp limit between the scales of the dorsal and ventral side. The radial shields are small, ca. 1/3 of disc radius and contiguous through the whole length (A. squamata disc).
This species is phosphorescent.
There are 3-4 pairs of short conical arm spines per arm segment. The tube foot pores are partially covered by 2 tentacle scales in the proximal part, and only 1 in the distal part of arm. The dorsal arm plates in the proximal part of the arm are broader than long, rounded-triangular. The ventral arm plates are triangular and truncated at the top (A. squamata arm).
The mouth shields are rhombic shaped. On top of the jaws there are paired infradental papillae and there are two outer mouth papillae on each side of jaw, contiguous with the infradental papillae. The outermost papilla is very broad, scale-like, and may, together with that of the opposite side, cover the outer part of the mouth slit completely. Two pairs of tube-feet within the mouth (A. squamata mouth).
This species is mainly found under stones and shells, but occasionally also on sandy bottoms, from the tide marks down to depths of about 250 m.
Cosmopolitan in temperate and warm temperate waters.