Conodonts are phosphatic, denticulated structures in the average size range from 0.1 to 1 mm. They grew by the centrifugal accretion of lamellae. Conodonts are a homogeneous group. Basic interpretations must apply to all kinds of conodonts. Internal and outer morphologic features indicate that they were skeletal elements designed to lend a certain limited rigidity to an organ in which the maximation of surface area was an advantage. Conodonts show evidence of muscle insertion. It is suggested that the muscles operated a tentacle apparatus. Platform and hibbardelliform (trichonodelliform) elements were probably located sagittally on opposite sides of the mouth; if, as a consideration of all known evidence seems to indicate, the conodonts were located close to, but not within, the mouth, this suggests that the mouth was surrounded by a lophophore-like organ. It is suggested that conodonts belonged to planktonic, wormlike lophophorates, with phosphatic lophophore supports. If this is true, they would not be closely related to any living group.