| E. Haeckel del. | Lagesse sc. |
We owe our first accurate knowledge of the Monorrhina, or Cyclostoma, to the great zoologist, Johannes Müller of Berlin; his classical work on the “Comparative Anatomy of the Myxinoida” forms the foundation of our modern views on the structure of the Vertebrate animals. He distinguished two distinct groups among the Cyclostoma, which we shall consider as sub-classes.
The first sub-class consists of the Hags (Hyperotreta, or Myxinoida). They live in the sea as parasites upon other fish, into whose skin they penetrate (Myxine, Bdellostoma). Their organ of hearing has only one annular canal, and their single nasal tube penetrates the palate. The second sub-class, that of Lampreys, or Prides (Hyperoartia, or Petromyzontia) is more highly developed. It includes the well-known Lamperns, or Nine-eyes, of our rivers (Petromyzon fluviatilis), with which most persons are acquainted. They are represented in the sea by the frequently larger marine or genuine Lampreys (Petromyzon marinus). The nasal tube of these single-nostriled animals does not penetrate the palate, and in the auricular organ there are two annular canals.
| SYSTEMATIC SURVEY | |||||||
| Of the 4 Main-classes, 9 Classes, and 26 Sub-classes of Vertebrata. Gen. Morph. vol. ii. Plate VII. pp. 116-160. | |||||||
| I. Skull-less (Acrania), or Tube-hearted (Leptocardia). Vertebrata without head, without skull and brain, without centralized heart. | |||||||
| 1. Skull-less (Acrania) | I. Tube-hearted Leptocardia |
| 1. | Lancelet | 1. | Amphioxus | |
| II. Animals with skulls (Craniota) and with thick-walled hearts (Pachycardia). Vertebrata with head, with skull and brain, with centralized heart. | |||||||
| Main-classes of the Skulled Animals. | Classes of the Skulled Animals. | Sub-classes of the Skulled Animals. | Systematic Name of the Sub-classes. | ||||
| 2. Single-Nostriled Monorrhina |
| II. Round mouths Cyclostoma |
| 2. | Hags, or Mucous Fish | 2. | Hyperotreta (Myxinoida) |
| 3. | Lampreys, or Pride | 3. | Hyperoartia (Petromyzontia) | ||||
| 3. Non-amnionate Anamnionata |
| III. Fish Pisces |
| 4. | Primæval fish | 4. | Selachii |
| 5. | Ganoid fish | 5. | Ganoides | ||||
| 6. | Osseous fish | 6. | Teleostei | ||||
| IV. Mud-fish Dipneusta |
| 7. | Mud-fish | 7. | Protopteri | ||
| V. Sea-dragons Halisauri |
| 8. | Primæval dragons | 8. | Simosauria | ||
| 9. | Snake-dragons | 9. | Plesiosauria | ||||
| 10. | Fish-dragons | 10. | Ichthyosauria | ||||
| VI. Batrachians Amphibia |
| 11. | Mailed Batrachians | 11. | Phractamphibia | ||
| 12. | Naked Batrachians | 12. | Lissamphibia | ||||
| 4. Amnion Animals Amnionata |
| VII. Reptiles Reptilia |
| 13. | Primary reptiles | 13. | Tocosauria |
| 14. | Lizards | 14. | Lacertilia | ||||
| 15. | Serpents | 15. | Ophidia | ||||
| 16. | Crocodiles | 16. | Crocodilia | ||||
| 17. | Tortoises | 17. | Chelonia | ||||
| 18. | Flying reptiles | 18. | Pterosauria | ||||
| 19. | Dragons | 19. | Dinosauria | ||||
| 20. | Beaked reptiles | 20. | Anomodontia | ||||
| VIII. Birds Aves |
| 21. | Long-tailed | 21. | Saururæ | ||
| 22. | Fan-tailed | 22. | Carinatæ | ||||
| 23. | Bush-tailed | 23. | Ratitæ | ||||
| IX. Mammals Mammalia |
| 24. | Cloacal animals | 24. | Monotrema | ||
| 25. | Pouched animals | 25. | Marsupialia | ||||
| 26. | Placental animals | 26. | Placentalia | ||||
