Delectopecten thermus, or the thermal glass scallop, has a shell that is not quite circular with an asymmetrical hinge, according to the study. The shell can reach up to 0.4 inches long ...
When a chalupa is shaped this way, it's one of the easiest ways to tell it apart from a tostada, which is always a flat, circular shell. The texture is also different, as tostada shells are made ...