These contain a coiled fiber that can be extruded suddenly. Some nematocysts contain toxic substances and are defense mechanisms, while others are adhesive, helping to anchor the animal or to entangle prey. The motile jellyfish, or medusoid form, is flattened, with the tentacles usually located at the body margin. The medusoid's convex aboral surface is oriented upward, and the concave oral surface is oriented downward. With few exceptions, the cnidarians are marine.
Cnidarians are carnivorous, the major part of their diet consisting of crustaceans.
Animals in this phylum have no specialized excretory or respiratory organs and posess a primitive nervous system. Both sexual and asexual reproduction occur. There are three classes of cnidarians. Listing from Electric Library , a pay service. No relevant pictures or maps found.