Their bodies tend to be dorso-ventrally flattened, they usually have five pairs of gill slits and a large mouth set on the underside of the head.
ðɛɹ bˈɑːdiz tˈɛnd təbi dˈoːɹsoʊvˈɛntɹəli flˈæʔn̩d, ðeɪ jˈuːʒuːəli hæv fˈaɪv pˈɛɹz ʌv ɡˈɪl slˈɪts ænd ɐ lˈɑːɹdʒ mˈaʊθ sˈɛt ɔnðɪ ˌʌndɚsˈaɪd ʌvðə hˈɛd.