The heterogeneous families constituting the order Picariæ may be conveniently arranged as follows:
| Sub-order— Scansores. |  | 51. Picidæ | Woodpeckers. |
| 52. Yungidæ | Wrynecks. | ||
| 53. Indicatoridæ | Honey-guides. | ||
| 54. Megalæmidæ | Barbets. | ||
| 55. Rhamphastidæ | Toucans. | ||
| 56. Musophagidæ | Plantain-eaters. | ||
| 57. Coliidæ | Colies. | ||
| 58. Cuculidæ | Cuckoos. | ||
| Intermediate | 59. Leptosomidæ | The Leptosoma. | |
| Sub-order— Fissirostres. |  | 60. Bucconidæ | Puff-birds. |
| 61. Galbulidæ | Jacamars. | ||
| 62. Coraciidæ | Rollers. | ||
| 63. Meropidæ | Bee-eaters. | ||
| 64. Todidæ | Todies. | ||
| 65. Momotidæ | Motmots. | ||
| 66. Trogonidæ | Trogons. | ||
| 67. Alcedinidæ | Kingfishers. | ||
| 68. Bucerotidæ | Hornbills. | ||
| 69. Upupidæ | Hoopoes. | ||
| 70. Irrisoridæ | Promerops. | ||
| 71. Podargidæ | Frog-mouths. | ||
| 72. Steatornithidæ | The Guacharo. | ||
| 73. Caprimulgidæ | Goatsuckers. | ||
| 74. Cypselidæ | Swifts. | ||
| 75. Trochilidæ | Humming-birds. | ||
The Psittaci or parrot tribe are still in a very unsettled state of classification; that recently proposed by Professor Garrod differing widely from the arrangement adopted in Dr. Finsch's monograph of the order. Taking advantage of the researches of these and other authors, the following families are adopted as the most convenient in the present state of our knowledge:
| 76. Cacatuidæ | The Cockatoos. |
| 77. Platycercidæ | The Broad-tailed Paroquets of Australia. |
| 78. Palæornithidæ | The Oriental Parrots and Paroquets. |
| 79. Trichoglossidæ | The Brush-tongued Paroquets and Lories. |
| 80. Conuridæ | The Macaws and their allies. |
| 81. Psittacidæ | The African and South American Parrots. |
| 82. Nestoridæ | The Nestors of New Zealand. |
| 83. Stringopidæ | The Owl-parrots of New Zealand. |
The Columbæ, or pigeons, are also in a very unsatisfactory state as regards a natural classification. The families, sub-families, and genera proposed by various authors are very numerous, and often quite irreconcilable. I therefore adopt only two families; and generally follow Mr. G. R. Gray's hand-list for the genera, except where trustworthy authorities exist for a different arrangement. The families are:
| 84. Columbidæ | Pigeons and Doves. |
| 85. Dididæ | The extinct Dodo and allies. |
The Gallinæ, or game-birds, may be divided into seven families:
| Fam. | Sub-fam. | ||
| 86. Pteroclidæ | Sand-grouse | ||
| 87. Tetraonidæ | Partridges and Grouse. | ||
| 88. Phasianidæ |  | Pavoninæ | Peafowl. |
| Lophophorinæ | Tragopans, &c. | ||
| Phasianinæ | Pheasants. | ||
| Euplocaminæ | Fire-backed Pheasants, &c. | ||
| Gallinæ | Jungle-fowl. | ||
| Meleagrinæ | Turkeys. | ||
| Numidinæ | Guinea-fowl. | ||
| 89. Turnicidæ | Hemipodes. | ||
| 90. Megapodiidæ | Mound-makers. | ||
| 91. Cracidæ |  | Cracinæ | Curassows. |
| Penelopinæ | Guans. | ||
| Oreophasinæ | Mountain-pheasant. | ||
| 92. Tinamidæ | Tinamous. | ||
The Opisthocomi consist of one family containing a single species, the "Hoatzin" of Guiana.
Family 93. Opisthocomidæ.