Grazing is facilitated by powerful muscles in large buccal mass, and by rust-coloured iron-reinforced teeth on long radula with plentiful replacements for worn teeth.
1: posterior of large buccal mass.
2: anterior part of pink buccal mass discernible through translucent head.
3: pale posterior of translucent radular sac (length 22mm) near buccal mass as sac folded back on itself to fit inside body (shell length 24.7mm).
4: as 3 but with radula removed from body.
5: anterior of radula/radular sac that was curved over buccal mass and concealed when in body (above).
6: anterior of radula (enlarged) protruded from sac for use in grazing rock surface.
7: hyaline shield (damaged, see 32 Patella depressa. Odontophore. Lleyn, Wales. September 2015. for undamaged example on P. depressa).
Lengths of radulae as % of shell length (Fretter & Graham 1962, p.172) :
P. ulyssiponensis 80-140% (overlap with P.vulgata range).
P. vulgata 113-230%
P. depressa 140-270%

The radula pictured above was 89% of shell length; the shortest in a sample of eight from the same site (range 89-108.6%, mean 99.1%). Radular lengths of many mollusc species vary with season and other environmental factors (Goshima et al. 2002) so they should not be relied on alone for identification.

OTHER SPECIES ALBUMS
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