In situ shot of the population Don took microscopic shots of at http://www.inaturalist.org/observations/2437251
More like H. minimum, but has that same sinuate aperture as the one I saw at Salt Point.
Copying from my analysis of Don's observation of the same individual: Roth and Sadeghian list V. megasoma, V. embertoni, and V. eritrichius (redescriptions or original descriptions with photos linked).
Of V. embertoni Roth and Miller wrote, "The large, depressed shell, sparse setation, very narrow umbilicus, and granular surface texture distinguish V. embertoni from most other species in northern California." To me, the setation looks pretty dense on this, but it's kind of a relative statement. It looks sort of granular, but maybe that's just the setae. Certainly looks depressed.
For the other two they write, "There appear to be no shell characters that will always separate V. eritrichius from V. megasoma." So maybe these just can't really be ID'd without dissection in Mendocino County.
See also Don's killer photos of the same at http://www.inaturalist.org/observations/2437117
I don't recall it being particularly foul-smelling. Didn't taste.
Hmph. Probably arrosa, but has hints of the beaded sculpture that would suggest nickliniana.
Growing on the ground in a wet ditch, did not see any reproductive structures, but maybe those bumps will become some.
Could be a juvenile H. minimum but the sculpture looks really different.
Maybe 10-15 mm long. Terrifying.
Small, maybe 5-8 mm, found under a log. Probably an unidentifiable juvenile Vespericola.
Seemed to be growing out of the moss, but maybe out of the soul.