After that post, several people wrote to say that they had seen these barnacles north of San Francisco this year. These are important records for this species in north-central California, so it seemed worth sharing them with you!
#1 — Hollis discovered this specimen at Stinson Beach during the winter:
#2 — Jim encountered several nice specimens at Salmon Creek Beach in Bodega Bay this summer:
And here's one more — a picture I took at Abbotts Lagoons (Point Reyes) in November 2015. Because there are hydroids growing on the barnacle, it makes it harder to identify the species, but I think it's likely this is also Paraconcavus pacificus:
Keep your eyes open for other examples. Who can find the furthest north record? Could they be at Manchester, MacKerricher, or even further north?
P.S. Many thanks to Hollis, Jim, and Megan for sharing their observations and wonderful photographs.