of the United States. 11 
View of the Natural Families of the System adopted in the 
classification of the North American Birds • 
Birds are vertebrated, warm-blooded, oviparous animals, 
formed for flying ; breathing by lungs : lungs undivided, 
attached to the ribs, covered by a membrane perforated with 
large holes ; heart bilocular and biauricular ; a corneous 
edentate bill ; skin feathered ; two wings and two feet. 
In the present state of the science, they form the second 
class of the first type of the animal kingdom. 
SUBCLASS L 
Hind toe articulated on the same plane with the fore toes, 
and bearing on the ground its whole length ; formed for 
grasping . 
ORDER I. ACCIPITRES. 
Feet ambulatory : bill hooked, with a cere : nails retractile. 
1. Vulturini- Head naked. 
% Rapaces. Head feathered. 
* Diurni. Eyes lateral. ** Nocturni. Eyes in front. 
ORDER II. PASSERES. 
Feet ambulatory, gressorial, or scansoriah 
TRIBE I. SCAJYSORES. Toes two before, and two behind, 
§ Anterior toes divided, or united only at base. 
3. Psittacini. Bill hooked, with a cere : none of the toes 
versatile. 
4. Frugivori. Outer hind toe versatile, connected with the 
fore toes by a membrane. 
5. Amphiboli. Outer hind toe versatile, free. 
* Bill ciliated. ** Bill not ciliated. 
6. Sagittilingues, Bill straight ; none of the toes versatile. 
