This book on ancient fishes unites the work of many specialists coming from different areas of biology. Hagfishes, lungfishes, Chondrosteans, and Holosteans constitute the main subject of study. Fossil records and extant species are compared to establish the conservation or the degeneration of specific characters. However, phylogenetic relationships have mostly been revisited in the light of new molecular and developmental data. The morphology of several organs is also revisited. This volume includes a phylogenetic account of the cardiac outflow tract, and the particulars of the heart and circulation in lungfishes. The control of breathing and the lung-swim bladder issue is discussed. The developmental anatomy of the sturgeon gut and accounts of the gut structure in lungfishes and garfishes are also included. Biochemical and physiological aspects of the behavior of lungfishes and gars are presented. Reports on the fish olfactory system, and on the amazing slime glands of hagfishes, are also covered.