Inoceramus are one of the most widespread and commonly found Mesozoic marine bivalves, ranging from the Early Jurassic to the Late Cretaceous. They are found in deposits all over the world, and can be small, or huge. So show us your Inos!
Here are two I have found.
The first is a plate with two of them from Holzmaden, where they are extremely common. The second is a larger weathered one from a local State Park tide pool. ( Of course, I didn’t collect it.)