All these shells and fragments were found during the afternoon low tide along the stretch of beach north of Moonlight, which is technically in Leucadia.
Sea Otter eating geoduck clam it had caught in shallow water near harbor entrance, we saw them catch several over a period of about 45 minutes. Mother was sharing with young sea otter.
Pacific Geoduck siphon
Don't see these fragments often, but I think this is distinctive enough.