[1] L. scabra grows to a length of about thirty-five millimetres and has conspicuous rugged radial ribs with darker-coloured interspaces and a boldly scalloped margin.

[3] L. scabra is found on the Pacific coast of North America from Cape Arago, Oregon to southern Baja California.

[4] At Mission Point on the California coast, L. scabra coexists with the similar species, Lottia digitalis, but each occupies a slightly different habitat.

L. digitalis clump together more often, prefer wave-exposed areas, occupy sites further up the shore and are seldom found in rock pools.

The differences in micro-habitat may be explained by its greater tolerance of exposure to desiccation during low tides in less protected sites because it is able to retain water better.

[5] In an experiment, when these two species were caged together with only vertical surfaces available, it was found that L. scabra grew at a much slower rate and achieved a much smaller maximum size than similar limpets in control plots.

It seems that the ability of L. digitalis to respond to seasonal changes by moving up and down the shore and utilising resources better give it an edge over the more static species which remains for life in its restricted home range.