Myxinomorphi (mix-I-no-MOR-fi) is derived from two Greek roots that mean slime or mucus forms [mucus = μύξα (myxa) + forms = μορφή (morphe)].  

The name of the group comes from the ability of living taxa to exude copious amounts of slime when disturbed.  This disgusting habit has earned them the name of hagfish.  Typically, they live in burrows on the ocean floor where they feed on carrion and invertebrates.  The mouth is surrounded by tentacles and contains bony plates covered with keratin toothlets.  Though jawless, they can grasp prey by protruding the mouth, which allows the toothlets to hold by a pinching action.  Developmental work on extant hagfishes suggests that their primitive nature is a holdover rather than a simplification and loss of structure.

The myxinomorphs resemble the Petromyzontomorphi (lampreys) which also have eel-like bodies with no jaws, no body armor, or paired fins.  However, the two groups do exhibit fundamental differences in the structures of their inner ears and in the ways that they move water into the pharynx and the gill pouches.  The most important difference is that hagfish have no vertebrae, although they do have crania.  Thus, the hagfishes are basal craniates, but they are not vertebrates.

Extinct taxa from the lower Cambrian have features that ally them with the hagfish.  Detailed fossils of Myllokunmingia [see the article from Science News (1999)] are interpreted to have gill pouches like the hagfish.  In addition, they also have square cartilaginous structures along the notochord which might have been the precursors to vertebrae.  All in all, they are the craniates that most closely resemble the Cephalochordata, the sister group to the Craniata.