hˈɛmɪsˌaɪklæspiz ɔːɹ sˈɛmɪsˌɜːkəl plˈeɪt ɪz ɐn ɛkstˈɪŋkt dʒˈɛnəs ʌv pɹˈɪmᵻtˌɪv dʒˈɔːləs fˈɪʃ, klˈoʊsli ɹᵻlˈeɪɾᵻd tə sˈɛfɐlˌæspiz, ðæt lˈɪvd ɪnðə lˈeɪt sɪlˈʊɹɹiən pɹˈɪdɑːli tə dɛvˈoʊniən pˈiəɹɪəd ɪn wʌt ɪz nˈaʊ jˈʊɹɹəp ænd nˈɔːɹθ ɐmˈɛɹɪkə.
Hemicyclaspis ( or 'semicircle plate') is an extinct genus of primitive jawless fish, closely related to Cephalaspis, that lived in the Late Silurian (Pridoli) to Devonian period in what is now Europe and North America.