Geography: In The World's Oceans, There Are: 58 Species Of Sea Grasses: Less Than 1,000 Species Of Cephalopods (Squids, Octopi, And Pearly Nautiluses): 1,000 Species Of Sea Anemones: 1,500 Species Of Brown Algae: 7,000 Species Of Echinoderms (Starfishes, Sea Urchins, Sea Cucumbers, And Sea Lilies): 13,000 Species Of Fishes: And 50,000 Species Of