On limpets, Nucella usually bore into pedal-retractor muscle, see 40dNl 40d Nucella lapillus bore-hole viewed from interior of Patella vulgata (33mm long). Lleyn, North Wales. September 2015. , or central area enclosed by it, where radula can reach nutritious viscera. Of 73 vacant bored-shells examined in Guernsey only 7% of holes were into viscera-free periphery distal of the muscle, though periphery was 52% of area of shells (Flint, 2001).
Of 42 bored Patella shells only one was less than 35mm long, probably because smaller shells can be dislodged by Nucella without boring.
Unlike Mytilus, there was no decline in predation holes in very large Patella ; holes in 20% of 137 shells length 35 to 49.9mm, and 38% of 34 shells length 50mm or more.

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