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 ] Pi cumnus (22 sp.), Tropical South America to Hon- 
duras ; ( 2113 ) Vivia, (1 sp.), Himalayas to East Thibet ; ( 2114 ) 
Sasia (2 sp.), Nepal to Java; ( 2115 ) Vevreamig, (1 sp.), West 
Africa ; Picoides (5 sp.), northern parts of Nearctic and Palie- 
arctic regions, and Mountains of East Thibet; Picus (42 sp.), 
the whole Palaearctic, Oriental, Nearctic, and Neotropical regions ; 
( 2123 ] Eyopicus (2 sp.), Himalayas and North China ; ( 2124 ) Yungi- 
picus (16 sp.), Oriental region, and to Elores, Celebes, North 
China, and Japan ; ( 2127 ~ 2129 ) Sphyrapicus (7 sp.), Nearctic re- 
gion, Mexico, and Bolivia; ( 213 °— 2133 2139 ] Campephilus (14 sp.), 
Neotropical and Nearctic regions ; Hylatomus (1 sp.), Nearctic 
region; ( 2137 214 °) Dryocopus (5 sp.), Mexico to South Brazil, 
Central and Northern Europe ; ( 2134 ) ReinwardUpicus (1 sp.), 
Penang to Borneo ; ( 21S5 2136 ) Venilia (2 sp.), Nepal to Borneo; 
Chrysocolaptes (8 sp.), India and Indo-Malaya; Dendropictts (16 
sp.), Tropical and South Africa ; H&micerms (5 sp.), Malabar and 
Pegu to Malaya ; Gecinus (18 sp.), Palaearctic and Oriental re- 
gions to Java; ( 2151 — 2156 ) Dendromus (15 sp.), West and South 
Africa, Zanzibar, and Abyssinia; ( 2157 “ 2159 ) Mulleripicus (6 sp.), 
Malabar, Pegu, Indo-Malaya, and Celebes ; Oeleus (17 sp.), Para- 
guay to Mexico ; Nmoceleus ( sp - 8833 ) Cuba ; ( 2162 ) Chrysoptilus (9 
sp.). Chili and South Brazil to Mexico ; Brachypternus (5 sp.), 
India, Ceylon, and China ; ( 2165 2166 ) Tiga (5 sp.), all India to 
Malaya ; ( 2167 ) Gecinulus (2 sp.), South-east Himalayas to Bur- 
mah ; Cmturus (13 sp.), Nearctic Eegion to Antilles and Vene- 
zuela ; Chloronerpes (35 sp.), Tropical America, Hayti ; ( 2m ) 
Xiphidiopicus (1 sp.), Cuba; Melanerpes (11 sp.), Brazil to 
