Nudibranch, slug, or larvae?

I found these cool tiny guys last night on a rope sponge. They were both on the on the same rope sponge at about 40' on Sunset House reef in Grand Cayman. The yellow and red creature looks like some kind of slug or larvae of something and the nudibranch looks like it might be some type of sea hare due to the shell looking thing on it's back. Any suggestions?

Number three appears to be a sea hare. Most likely Stylocheilus striatus

Cheers,

Marli

The first one looks somewhat similar to a turbellarian flatworm I photographed in the British Virgin Islands a while back. The picture is here: http://www.nhm.org/guana/bvi-invt/bvi-surv/othe-g01.htm One difference that I notice (besides the color pattern) is the presence of a narrow tail on yours which may make it a nemertean. I'll send a message to Nemertinator, a fellow with a fondness for all things nemer, for his opinion. He has much more experience than I with the unsegmented worms.

Yep, the last pic is definitely a sea hare. Just a week ago I saw a sea hare that was about 5'' long, quite a big meaty guy. Weird how they get so big after starting out so small. Leslie - thanks for your input. I knew you'd come up with something! You're awesome!! The yellow and red guy does look very similar to your pics except for the tail as you say.

Thankfully Jon agreed with me on turbellarian flatworm.

cheers, Leslie