CHAP. XVIII.] BIRDS. 303 



its extreme isolation, its great specialization of structure, its 

 abundant generic forms, and its wide distribution. It originated, 

 probably, in Central Asia, and passed through the Nearctic 

 region to South America, in whose rich and varied forests it 

 found the conditions for rapid development, and for the speciali- 

 zation of the many generic forms now found there. 



A large number of genera have been established by various 

 authors, but their limitations and affinities are not very well 

 made out. Those which seem best established are the fol- 

 lowing : — 



^2107 — 2112^ Picumnus (22 sp.), Tropical South America to Hon- 

 duras ; (2"3) Vivia (1 sp.), Himalayas to East Thibet; (^n*) 

 Sasia (2 sp.), Nepal to Java ; (J^^^) Verreauxia (1 sp.), West 

 Africa ; Picoides (5 sp.), northern parts of Nearctic and Palce- 

 arctic regions, and Mountains of East Thibet; Picus (42 sp.), 

 the whole Palsearctic, Oriental, Nearctic, and Neotropical regions ; 

 ^2123^ ffyopicus (2 sp.), Himalayas and North China ; (2^^*) Yungi- 

 picus (16 sp.). Oriental region, and to Flores, Celebes, North 

 China, and Japan ; (^127 - 2129-) Sphyrajpicus (7 sp.), Nearctic re- 

 gion, Mexico, and Bolivia ; (^^^^ ~ ^^^^ 2^^^) Campephihcs (14 sp.). 

 Neotropical and Nearctic regions ; Hylatomus (1 sp.), Nearctic 

 region; (^^^^ 2"°) Dryocopus (5 sp.), Mexico to South Brazil, 

 Central and Northern Europe ; (2^^*) Reinwardtipicus (1 sp.), 

 Penang to Borneo ; (^^^^ '^'^^) Venilia (2 sp.), Nepal to Borneo ; 

 Chrysocolaptes (8 sp.), India and Indo-Malaya; Dendi^opicus (16 

 sp.). Tropical and South Africa ; Hemicercus (5 sp.), Malabar and 

 Pegu to Malaya ; Gecinus (18 sp.), Palsearctic and Oriental re- 

 gions to Java ; (^^^^ — ^ise^ Dendromus (15 sp.). West and South 

 Africa, Zanzibar, and Abyssinia ; (^^^^ — 2^^^) Mulleripicus (6 sp.), 

 Malabar, Pegu, Indo-Malaya, and Celebes ; Celeus (17 sp.), Para- 

 guay to Mexico ; Nesoceleus ( ^p- ^^^^) Cuba ; (2^^^) Chrysoptilus (9 

 sp.). Chili and South Brazil to Mexico ; Brachypternus (5 sp.), 

 India, Ceylon, and China ; (^i^s 2166) ^-^^ (5 gp )^ ^11 India to 

 Malaya ; ("^^^) Gecinulus (2 sp.). South-east Himalayas to Bur- 

 mah ; Centurus (13 sp.), Nearctic Eegion to Antilles and Vene- 

 zuela ; Chloronerpes (35 sp.). Tropical America, Hayti ; (^I'^i) 

 Xiphidiopicus (1 sp.), Cuba; Melanerpes (11 sp.), Brazil to 



