Lampreys are a group of jawless fish comprising the order Petromyzontiformes. The adult lamprey is characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is probably derived from Latin lampetra, which may mean "stone licker", though the etymology is uncertain. Lamprey is sometimes seen for the plural form.
Lamprey
Mouth of a sea lamprey, Petromyzon marinus
Median section of Lamprey demonstrating internal anatomy
The cartilaginous skeleton of a lamprey washed up on a beach in North Carolina.
Agnatha is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct species. Among recent animals, cyclostomes are sister to all vertebrates with jaws, known as gnathostomes.
Agnatha
Image: Eptatretus hexatrema 15727711
Image: Pacific lamprey facing right
Image: Thyestes verrucosus 22DB