For beginner turtle enthusiasts who come across these terms and are unfamiliar with them, here’s the quick skinny. The Carapace is the upper part of a turtle’s shell, the “dome” some would say. For species with a flatter appearance, it also is referred to as simply the “top” of the shell.

The Plastron is the bottom part of the shell. Sometimes called the bottom “plate”. Whether it is concaved or flat, hinged or stationary, fully inclosing the turtles bottom (like a box turtle) or leaving lots of flesh exposed (like a musk turtle), it is still called the plastron.