Adults and egg masses (images 5 & 6).

In September 2019 I dissected the specimen shown in the 1st image here, and the shape of the gizzard plates (7th image), combined with the shell sculpture (8th image) reveal these to be P. auriformis as described by Gosliner (1995, Marine Biology 122:249-255) and Valdés, Cadien and Gosliner (2016, Zootaxa 4147 (5): 501–537). The dissected specimen was 22 mm long preserved, with a shell 13.5 x 9.8 mm, and three gizzard plates, with the longest 6.4 x 4.0 mm.

Just posterior to its gizzard plates the dissected specimen had a Haminoea vesicula about 6 mm long (9th & 10th images) it had consumed and whose shell it had crushed into fragments (not shown).

I had observed abundant P. auriformis in Coos Bay, Oregon near the end of the strong 1997-98 El Nino; interestingly the specimens here from Morro Bay were found near the end of the strong 2015-16 El Nino.