J/2 ZOOLOGICAL GEOGRAPHY. [part hi. 



soil of a large portion of it is very fertile, it is altogether well 

 adapted to support a varied fauna, as it does a most luxuriant 

 vegetation. Although many peculiar Neotropical types are 

 absent, it yet possesses an ample supply of generic and specific 

 forms ; and, as far as concerns birds and insects, is not perhaps 

 inferior to the richest portions of South America in the number 

 of species to be found in equal areas. 



Owing to the fact that the former Eepublic of Mexico 

 comprised much territory that belongs to the Nearctic region, 

 and that many Nearctic groups extend along the high-lands to 

 the capital city of Mexico itself, and even considerably further 

 south, there is much difficulty in determining what animals 

 really belong to this sub-region. On the low-lands, tropical 

 forms predominate as far as 28° N. latitude ; while on the 

 Cordilleras, temperate forms prevail down to 20°, and are found 

 even much farther within the tropics. 



Mammalia. — Very few peculiar forms of Mammalia are re- 

 stricted to tropical North America ; which is not to be wondered at 

 when we consider the small extent of the country, and the facility 

 of communication with adjacent sub-regions. A peculiar form 

 of tapir {Elasmognathus hairdi) inhabits Central America, from 

 Panama to Guatemala, and, with Myxomys, a genus of Muridae, 

 are all at present discovered. Bassaris, a remarkable form of 

 Procyonidge, has been included in the Nearctic region, but it 

 extends to the high-lands of Guatemala. Heteroniys, a peculiar 

 genus of • Saccomyidae or pouched rats, inhabits Mexico, 

 Honduras, Costa Pdca, and Trinidad. Five genera of monkeys 

 extend here, — Aides, My cetes, Cchus, Nyctipithccus, and Saimiris; 

 the two former alone reaching Mexico, the last only going as far 

 as Costa Eica. Other typical Neotropical forms are Galera, the 

 tayra, belonging to the weasel family ; Nasua, the coatimundi ; 

 Dicotyles, the peccary ; Cercolabes, the tree porcupine ; Dasyprocta, 

 the agouti ; Coeloyenys, the paca ; Choloipus, and Arctopithecus, 

 sloths ; Cydothurus, an ant-eater ; Tatusia, an armadillo ; and 

 Biddphys, oppossum. Of Northern forms. Sorex, Vulpes, Lepus, 

 and Pteromys reach Guatemala. 



Birds. — The productiveness of this district in bird life, may 



