Trip to Cozumel - What are these creatures called?

[stronj1]

The nudibranch was about 3/4" long. The other was maybe 4" long - are there decorator clams? These were both taken in Cozumel last week.

 

[SubMariner]

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The nudibranch was about 3/4" long. The other was maybe 4" long - are there decorator clams? These were both taken in Cozumel last week.

I think the nudi is either a white spotted or freckled sea hare.

The "clam" appears to be a frond oyster because of the valve interlock zig-zag pattern. According to Paul Humann, they tend to be well camouflaged & overgrown by a number of organisms like encrusting sponges and in this case what appears to be young coral.

 

[LouisJ]

appears to be young coral.

Fire Coral.

 

[cgills]

The sea slug, or nudibranch, is an Elysia ornata or Ornate Elysia.

 

[stronj1]

Yes, the speckles seem to match that description. The coloring is a bit different in the Humann book but I just "googled" Elysia ornata and there is a picture there that matches the coloring of the one in the picture. Thanks a bunch!