| Sub-classes. | Orders. | |||
| I. | Squamata |  | 1. Ophidia | Serpents. |
| 2. Lacertilia | Lizards. | |||
| 3. Rhyncocephalina | The Hatteria. | |||
| II. | Loricata | 4. Crocodilia | Crocodiles. | |
| III. | Cataphracta | 5. Chelonia | Tortoises. | |
In the arrangement of the families comprised in each of these orders I also follow the arrangement of Dr. Günther and Dr. J. E. Gray, as given in the British Museum Catalogue, or as modified by the former gentleman who has kindly given me much personal information.
The Ophidia, or Snakes, form the first order and are classified as follows:—
| Fam. | ||||
| Innocuous Snakes |  | 1. Typhlopidæ |  | Burrowing Snakes. |
| 2. Tortricidæ | ||||
| 3. Xenopeltidæ | ||||
| 4. Uropeltidæ | ||||
| 5. Calamaridæ | Dwarf ground-snakes. | |||
| 6. Oligodontidæ. | ||||
| 7. Colubridæ | Colubrine Snakes. | |||
| 8. Homalopsidæ | Fresh-water Snakes. | |||
| 9. Psammophidæ | Desert-snakes. | |||
| 10. Rachiodontidæ. | ||||
| 11. Dendrophidæ | Tree-snakes. | |||
| 12. Dryiophidæ | Whip-snakes. | |||
| 13. Dipsasidæ | Nocturnal tree-snakes. | |||
| 14. Scytalidæ | ||||
| 15. Lycodontidæ | Fanged ground-snakes. | |||
| 16. Amblycephalidæ | Blunt-heads. | |||
| 17. Pythonidæ | Pythons. | |||
| 18. Erycidæ | Sand-snakes. | |||
| 19. Acrochordidæ | Wart-snakes. | |||
| Venomous Colubrine Snakes |  | 20. Elapidæ | Cobras, &c. | |
| 21. Dendraspididæ. | ||||
| 22. Atractaspididæ. | ||||
| 23. Hydrophidæ | Sea-snakes. | |||
| Viperine Snakes |  | 24. Crotalidæ | Pit-vipers. | |
| 25. Viperidæ | True vipers. | |||
The second order, Lacertilia, are arranged as follows:—
| Fam. | ||
| 26. Trogonophidæ | | Amphisbænians. |
| 27. Chirotidæ | ||
| 28. Amphisbænidæ | ||
| 29. Lepidosternidæ | ||
| 30. Varanidæ | Water Lizards. | |
| 31. Helodermidæ. | ||
| 32. Teidæ | Teguexins. | |
| 33. Lacertidæ |  | Land Lizards. |
| 34. Zonuridæ | ||
| 35. Chalcidæ. | ||
| 36. Anadiadæ. | ||
| 37. Chirocolidæ. | ||
| 38. Iphisadæ. | ||
| 39. Cercosauridæ. | ||
| 40. Chamæsauridæ. | ||
| 41. Gymnopthalmidæ | Gape-eyed Scinks. | |
| 42. Pygopodidæ | Two-legged Lizards. | |
| 43. Aprasiadæ. | ||
44. Lialidæ. | ||
| 45. Scincidæ | Scinks. | |
| 46. Ophiomoridæ | Snake-lizards. | |
| 47. Sepidæ | Sand-lizards. | |
| 48. Acontiadæ. | ||
| 49. Geckotidæ | Geckoes. | |
| 50. Iguanidæ | Iguanas. | |
| 51. Agamidæ | Fringed Lizards. | |
| 52. Chameleonidæ | Chameleons. | |
The third order, Rhyncocephalina consists of a single family:—
53. Rhyncocephalidæ The Hatteria of New Zealand.
The fourth order, Crocodilia or Loricata, consists of three families:—
| 54. Gavialidæ | Gavials. |
| 55. Crocodilidæ | Crocodiles. |
| 56. Alligatoridæ | Alligators. |