1) Class 2) Superclass agnatha 
Agnatha (Greek, `no jaws`) is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (cyclostomes) and extinct (conodonts and ostracoderms) species. The group excludes all vertebrates with jaws, known as gnathostomes. The agnathans as a whole are paraphyletic, because most extinct agnathans belong t.....
The agnatha are a branch of the sub-Phylum craniata group of animals. They are the lampreys and hagfishes. These are the most primitive of the Craniates. The mouth is round and not bounded by jaws. The brain is primitive.
[n] - superclass of eel-shaped chordates lacking jaws and pelvic fins: lampreys
superclass Agnatha noun superclass of eel-shaped chordates lacking jaws and pelvic fins: lampreys; hagfishes; some extinct forms
the class of vertebrates comprising the lampreys, hagfishes, and several extinct forms, having no jaws or paired appendages.