39 Testudinalia testudinalis. Great Cumbrae, Scotland. March 2016. © P. Lightfoot.

39 Testudinalia testudinalis. Great Cumbrae, Scotland. March 2016. © P. Lightfoot.

T. testudinalis feeds on diatoms, algae and other growths coating bedrock and boulders. Littoral specimens are often found on bare upright or overhanging rock surfaces during daylight, returning to feeding surfaces at night. Great Cumbrae, Scotland. © P. Lightfoot.

APPENDIX re range advance/retreat: flic.kr/p/2jW74ig

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