Spotting the Differences

You know those puzzles where you have to figure out the differences in the pictures? Use shell pictures and you pretty much know what I do when I hide at the museum. Can you tell the differences? These two are shells I collected in the last couple weeks from the C and D Canal. The one on the top is broken, but I was able to nail it down. Then I found the shell on the bottom. My first thought was that they were the same species. Since they are both less then 2 cm, I photographed them under my microscope to compare them. Ah, but the interior of the one on the bottom was dirty! I cleaned it under the microscope with a straight pin to discover some tell-tale structures. Once cleaned I could see that the interiors are very different. They aren't even in the same PHYLUM! (Remember the taxonomic tree: Kingdom, Phylum, Class, Order, Family, Genus, Species) The one on the top is a scallop with the auricles (the little wings on the sides of the beak) broken off, while the one on the bottom is a brachiopod I am still trying to identify. Many field guides only show the exterior view of clams and scallops, since the ornament is the most distinctive feature most of the time. Could you figure it out from the pictures?