As nouns the difference between cnidarian and siphonoglyph
is that
cnidarian is any of various invertebrate animals, such as jellyfish, hydras, sea anemones, corals and formerly sponges and ctenophores that belong to the phylum
Cnidaria while
siphonoglyph is a longitudinal flagellated chamber found in most cnidarians in the classes
Scyphozoa and
Anthozoa, extending from the mouth towards the colenteron (body cavity).