ebarbs

This is not Haliotis varia, as that species would not be found anywhere near Catalina. It is more than likely Haliotis walallensis (Flat Abalone), but it would be much easier to tell by seeing it live. Were these shells purchased or found?

This isn't a Sea Angel (pteropod) actually Amanda. It is a nudibranch (dendronotid) in the genus Melibe. Very cool though!

Marlon: Diadema savignyi has much loner spines in proportion to its test.It also does not have two separate sets of spines as in the pictured E. diadema (thick, longer spines, and the smaller set of very thin, sharp spines).

Great shots! But like Gerardo had mentioned, this is a polyclad, not a nudibranch. Unfortunately polyclads are not opisthobranchs

That is actually a polyclad flatworm! I am unsure of the specific species, but t believe it is in the Thysanozoon genus. The rhinophore resembling structures towards the front are psuedotentacles used (possibly) to mimic nudibranchs.