Figure 3: Mixed bed of M. desolationis and A. ater. The specimens were found in mixed beds located at Port-aux-Français in the Kerguelen Islands. On the left, the blue mussel M. desolationis. Each valve is elongated with a relatively smooth external surface that displays concentric growth rings. The anterior end is pointed and the posterior end is well rounded. The dorsal margin is convex and the ventral is weakly concave. On the right, A. ater, also known as the ribbed mussel, or Cholga or Cholgua, in South America. Its shell is multiform, with a concave ventral edge in most of the specimens. The dorsal edge is notoriously more prominent towards the rear half leaflet. Externally, it presents concentric grooves growth and marked ribs radials with band width decreasing progressively with increasing size.