Hexanchidæ.—Family Chlamydoselachidæ.—Order Asterospondyli.—Suborder Cestraciontes.—Family Heterodontidæ.—Edestus and its Allies.—Onchus.—Family Cochliodontidæ.—Suborder Galei.—Family Scyliorhinidæ.—The Lamnoid, or Mackerel-sharks.—Family Mitsukurinidæ, the Goblin-sharks.—Family Alopiidæ, or Thresher-sharks.—Family Pseudotriakidæ.—Family Lamnidæ.—Man-eating Sharks.—Family Cetorhinidæ, or Basking Sharks.—Family Rhineodontidæ.—The Carcharioid Sharks, or Requins.—Family Sphyrnidæ, or Hammer-head Sharks.—The Order of Tectospondyli.—Suborder Cyclospondyli.—Family Squalidæ.—Family Dalatiidæ.—Family Echinorhinidæ.—Suborder Rhinæ.—Family Pristiophoridæ, or Saw-sharks.—Suborder Batoidei, or Rays.—Pristididæ, or Sawfishes.—Rhinobatidæ, or Guitar-fishes.—Rajidæ, or Skates.—Narcobatidæ, or Torpedoes.—Petalodontidæ.—Dasyatidæ, or Sting-rays.—Myliobatidæ.—Family Psammodontidæ.—Family Mobulidæ. 523

CHAPTER XXXI. THE HOLOCEPHALI, OR CHIMÆRAS. The Chimæras.—Relationship of Chimæras.—Family Chimæridæ.—Rhinochimæridæ.—Extinct Chimæroids.—Ichthyodorulites. 561 CHAPTER XXXII. THE CLASS OSTRACOPHORI. Ostracophores.—Nature of Ostracophores.—Orders of Ostracophores.—Order Heterostraci.—Order Osteostraci.—Order Antiarcha.—Order Anaspida. 568 CHAPTER XXXIII. ARTHRODIRES. The Arthrodires.—Occurrence of Arthrodires.—Arthrognathi.—Anarthrodira.—Stegothalami.— Arthrodira.—Temnothoraci.—Arthrothoraci.—Relations of Arthrodires.—Suborder Cycliæ.—Palæospondylus.—Gill on Palæospondylus.—Views as to the Relationships of Palæospondylus: Huxley, Traquair, 1890. Traquair, 1893. Traquair, 1897. Smith Woodward, 1892. Dawson, 1893. Gill, 1896. Dean, 1896. Dean, 1898. Parker & Haswell, 1897. Gegenbaur, 1898.—Relationships of Palæospondylus 581 CHAPTER XXXIV. THE CROSSOPTERYGII. Class Teleostomi.—Subclass Crossopterygii.—Order of Amphibians.—The Fins of Crossopterygians.—Orders of Crossopterygians.—Haplistia.—Rhipidistia.—Megalichthyidæ.—Order Actinistia.—Order Cladistia.—The Polypteridæ 598 CHAPTER XXXV. SUBCLASS DIPNEUSTI, OR LUNGFISHES. The Lungfishes.—Classification of Dipnoans.—Order Ctenodipterini.—Order Sirenoidei.—Family Ceratodontidæ.—Development of Neoceratodus.—Lepidosirenidæ.—Kerr on the Habits of Lepidosiren 609