In the photo above, the front end is to the right and the back end is to the left (with the notch). Chitons are marine molluscs with eight partially overlapping shell plates. The plate at the front end is called a head plate, and the plate at the back end is called a tail plate. Here's a zoomed in view of the head plate with attractive green radiating tubercles (bumps).
If you look along the edge of this chiton, you can see lots of spiky bristles (they're formally called setae).
These bristles are (supposed to be) useful for identifying chitons. I've isolated one in case someone can help me with figuring out this species.
I searched through some of my older chiton pictures to see if I had any images of chitons that looked similar to this one. No luck, but I did find a lot of other beautiful chitons that I haven't identified yet. (See below for an example.)
I think I've photographed at least 15 different species of chitons on Bodega Head so far, with more to come!