Question

1. There are starfish, jellyfish, sea anemones, sea horses, sea urchins, etc in the ocean.

2. There are starfishes, jellyfishes, sea anemones, sea horses, sea urchins, etc in the ocean.

(Which expression is correct?)

Answer 1

Common usage for the plural of fish, starfish, and jellyfish is the same: fish, starfish, and jellyfish.

So 1) is correct. I remember in the King James version of the Bible, fishes was plural, but no longer.

Answer 2

etc. is an abbreviation and has a period following.

Answer 3

Since "etc." is an abbreviation for the Latin, "et cetera," it is typically followed by a period.

I hope this helps a little more. Thanks for asking.

Answer 4

In addition to adding a period after "etc." you also need to add a comma since you are ending a series.

"...sea urchins, etc., in the ocean."

From http://www.bartleby.com/141/strunk.html
in Section 3:
"The abbreviations etc. and jr. are always preceded by a comma, and except at the end of a sentence, followed by one."