Help with Identifying these please!

[autographcollector11]

Can anyone help identify these? What are they? 2 of the pictures are of the same item-showing both sides. It is sandstone. They were found on the west coast.

 

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[High Plains Digger]

It looks like limpet shells and perhaps a barnacle tube, fossilized. Or lots of other animals that lived in tubes like that. Must be billions and billions at least, of different critters.