SYSTEMATIC SYNOPSIS 



OF 



l^ORTT-I AMERICAN BIRDS. 



Subclass I. AVES AERE^, or INSESSOEES. 



AERIAL BIRDS, or PERCIIERS. 



The first and liighest one of three primary divisions of the classf Aves, embrac- 

 ing all existing birds down to the GaUince. 



The knee and part of the thigh are free from the body, and the leg is almost 

 always feathered to or beyond the tibio-tarsal joint. With rare exceptions, the 

 toes are all on the same level, and touch the support throughout ; being thus fitted 

 for grasping ox perching . In other respects the members of this great group are too 

 various to be defined by external characters, unless it be negatively, in the absence 

 of the special features of the other two groups. They are Altrices. They are now 

 usually divided into Jive Orders, of which the first is the 



Order PASSEEES. Perchers Proper. 



The feet are jjerfectly adapted for grasping by the length and low insertion of 

 the hind toe, great power of opposing which to the front toes, and great mobility 

 of wliich, are secured by separation of its principal muscle from that that bends 

 the other toes collectively. The hind toe is always present, and never turned for- 



*North of tlie present Mexican Boundai-y; inclusive of Lower California; exclusive of Greenland. 



t As commonly received, "witliout recognizing, hoivever. the fossil Archceopteryx (see Introd.§p.l2) a meso- 

 zoio bird, which probably alone represents a primary gi-oup Sanrurw! admitting which, some high authorities 

 then divide all existing birds into two other primary groups, liatitw (Ostriches), in which the sternum has no 

 keel, and Carinatce, embracing all other birds. On this basis, our Aves aereoa would represent a group of less 

 value than a subclass ; and I desire to be understood as using this term provisionally, in a conventional sense. 



(69) 



