Here is a nice view of a black leather chiton, Katharina tunicata, on an encrusted boulder way out in the infralittoral fringe. Besides the main attraction, a lot is going on on this patch of rock; predominantly a good showing of encrusting and branching corallines, typical in the lowest intertidal and shallow subtidal zones.
The specimen on display here is slightly over 3 inches long, but Katharina can grow to over 5 inches. Black leathers are hefty but by no means the biggest TOS chiton. They move around slowly, scraping algae and other organisms off the surface of their rock. This one’s head is pointed down, and its mouth, which is on the underside, is pretty much under the lowest valve (shell) – the head valve. The head valve is the first in a sequence of eight valves. Beachcombers know the valves as butterfly shells.
To learn more about Katharina tunicata, check out the Pacific Rocky Intertidal Monitoring: Trends and Synthesis species account.
I updated this post on September 27, 2022.