Acanthochitona fascicularis, the Velvety mail shell,[1] is a common chiton in the family Acanthochitonidae.

The keel shows longitudinal ridges and appears coarsely granular due to densely packed, oval or rounded and evenly arranged dorsal papillae.

The girdle contains 18 tufts of bristles (maximum length : 1.5 mm), one on each side at the back of the plates.

The sculpture of the valves consists of a cover with densely packed, backward-pointing spines that are regularly distributed and give a velvety feel when touched.

[2] This species can be confounded with Acanthochitona crinita, but this last one is smaller (about 30 mm) and the granules on the dorsal plates are large, flat topped and pyriform and unevenly spaced.