3. Superclass Agnatha Classes Myxini and Cephalaspidomorphi about 84 species lack a jaw paired fins no scales relationships among agnathans is uncertain

4. Class Myxini (hagfishes) teeth on tongue naked skin no paired appendages fibrous and cartilagenous skeleton 2 chambered heart (ventricle, atrium) pronephritic kidney

5. no stomach nervous system no cerebellum eyes degenerate 10 pairs of cranial nerves no larval stage- direct development Class Myxini (hagfishes)

6. Class Cephalaspidomorphi = Petromyzontides (Lampreys) no jaws; –mouth with circular sucker like structure with lots of teeth Pineal eye; third eye for orientation

7. persistent notochord cartilaginous skeleton two median fins, no paired appendages 2 chambered heart –blood with specialized cells- leucocytes, nucleated erythrocytes Class Cephalaspidomorphi = Petromyzontides (Lampreys)

8. gills as adults mesonephritic kidney brain with 10 cranial nerves; small cerebellum present poikilothermic (cold blooded) Class Cephalaspidomorphi (Lampreys)

9. Life cycle Parasitic on fishes external fertilization metamorphosis Class Cephalaspidomorphi (Lampreys)

11. Lamprey larva hagfish have direct development; lampreys with ammocoetes larva