Neat how you can see the "ribs" inside.
Tiny (less than 1/4"), spreading everywhere on old sea lettuce. Each has a tiny reddish orange top.
Ascidiacea (commonly known as the ascidians or sea squirts) is a class in the Tunicata subphylum of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" made of the polysaccharide tunicin, as compared to other tunicates which are less rigid.