Quality
You have to use two axes to open these shellfish. That seems like overkill, but it is necessary. These particular shellfish are of very high quality meaning they won't open so easily.
Imagine the highest quality shellfish you've ever seen. They're hard, smooth, and basically impenetrable.
しつ, しち
None
None
You finally get all of the shellfish open and you're admiring their quality, when your shih tzu (しつ) jumps up on the table and gobbles them down. NO! You try to chase after the little dog, but it's too late. They're gone.
I guess your shih tzu knows good quality shellfish too. :(