Those look like cerith snail shells. Are you sure the snails are still in there? (i.e. can you see inside the hole?)...
If so, they really should be moving after a couple hours. How did you acclimate them?
I find I get a fairly low survival rate inside the first 24 hours. I scoop acclimate for about an hour or two, my acclimation cup floats in the tank water the entire time. usually the snails who live until the next morning, start moving around in the acclimation cup... Some snails are hardier than others, of course. Snails are typically shipped to the LFS without water, so depending on how they 'present the snails' to the customer, a good jag of them could be dead. If the employee just grabs a few shells, without looking for signs of life, you could easily get a handful of dead snails