It is found in western North America, from Vancouver Island south to central California, usually close to a shore.

The lower surface is whitish, tan or brown, minutely reticulate rugose, sometimes veined at ridge crests, darkening but not punctate.

[2][3] Platismatia stenophylla is found in western North America, from Vancouver Island south to central California, usually close to a shore.

[2] It has a largely sympatric range with P. herrei on the West Coast of North America, although P. stenophylla has a slightly smaller distribution.

[3] Further research with increased sampling and additional genetic loci is needed to fully resolve the relationship between P. stenophylla and P. herrei and to better understand their distribution patterns.