Acanthochitona fascicularis, Dorset (lower) and A. crinita, Cornwall (upper) girdle tufts. © I.F. Smith and N. Ward.
Each of the eighteen tufts on the girdle of:
A. fascicularis have 60 to 120, thin (13µm to 24µm diameter) , straight, needle-like, translucent spicules up to about 2mm long
A. crinita have 25 to 80 substantial (40µm to 45 µm diameter), slightly curved, translucent spicules up to about 1mm long
(Schmidt-Petersen et al., 2015 ).

On both species, spicule colours vary so they are not diagnostic 25Af 25 Acanthochitona fascicularis . Spicules do not grow at the same rate as body length and often look relatively shorter on large old specimens.

KEY ID FEATURES : 01 Acanthochitona fascicularis