INTRODUCTION. vn 



researches should not be confined by the artificial boundaries 

 of States — ^which may be frequently changed — but by those 

 divisions the limits of which are fixed by nature, and where 

 new forms mark the effects of a low latitude and warm 

 cUmate. In this way America is divided into three parts: 

 — North America, which includes all that country lying 

 north of the tropics ; Central or Tropical America, the 

 countries within the tropics ; and South America, all that 

 coimtry south of the tropic of Capricorn. 



Within the tropical region peculiar forms are presented in 

 every department of nature, — we need only instance the 

 Monkey tribe among the animals, the Parrots among the birds, 

 and the Pahns among the plants. 



A considerable portion of the country to which our attention 

 has been directed, is at the present period an uncultivated and 

 almost unexplored wild, roamed over by ferocious beasts and 

 warlike tribes of Indians. 



The objects of our search, Quadi-upeds, are far less numer- 

 ous than birds at all times, and are, moreover, generally 

 -nocturnal in their habits, and consequently obtained with far 

 greater difficulty than the latter. 



Although the Genera may be easily ascertained, by the 

 forms and dental an-angements peculiar to each, many species 

 so nearly approach each other in size, while they are so 

 variable in colour, that it is exceedingly difficult to separate 

 them, especially closely aUied squirrels, hares, mice, shrews, 

 &c., with positive certainty. 



"We are, therefore, far from supposing that our work will be 

 free fi-om errors, or that we shall be able to figure and^ 

 describe every species that may exist within our range; al- 



