The Devonian period was 410-360 million years ago and it is known as the "Age of Fish" (Huges, 1996). The first backboned "fish" were the Aganthans, which are commonly called jawless fish (Huges, 1996). Agnathans live today as hagfish and lampreys, but they do not resemble ancient Agnathans (Hamlin, 1999). The Agnathans lived from 510 to 350 million years ago (Huges, 1996). These fish, since they did not have a jaw, sucked food in through a hole in their heads (BBC, 1998). One type of Agnathan was the Hemicyclasis, which had only one nostril and a bony head shield (BBC, 1998).