108 ORNITHOLOGY AND OOLOGY. 



ORDER III. INSESSORES. PERCHERS. 



In accordance with the views of many systematic writers, 

 it may perhaps be as well to retain an order Insessores, and to 

 place in it the Strisores, Clamatores, and Oscines as sub-orders. 

 The characters of the order will then consist chiefly in the posses- 

 sion of three toes in front and one behind (or, at least, never with 

 two toes directed backwards), as in Scansores. The claws are not 

 retractile, nor the bill with a cere, as in the Raptores ; nor is the 

 hind toe situated appreciably above the plane of the others, as in 

 Rasores, Grallatores, and Natatores. 



The hind toe of the Insessores corresponds to the thumb or 

 inner toe of the mammals, and is usually quite short. The joints 

 of the anterior toes generally follow the law of number character- 

 istic of birds ; namely, two to the hinder, three to the inner, four 

 to the middle, and five to the outer toes : but a deviation is seen in 

 some Strisores, where there are sometimes but three joints each to 

 the anterior toes, and sometimes only four in the outer. The tarsi 

 are generally covered anteriorly with plates, and furnished behind 

 with granulations or small scales, or else with two long plates 

 covering the sides, the latter feature especially characteristic of the 

 Oscines, or singing-birds : in the latter alone is the tarsus some- 

 times covered anteriorly with a single plate. Sometimes the tarsus 

 is entirely or partly naked, or destitute of plates altogether. 



The carpal joint or the hand part of the wing is in most 

 Insessores furnished with ten quills (primaries), although the first 

 quill is sometimes very short, or even entirely wanting, as in many 

 Oscines. The fore-arm has from six (in the Humming-birds) to 

 thirteen quills, the average being eight or nine. 



There are certain peculiarities in the arrangement of he 

 wing coverts of the different sub-orders of Insessores, constituting 

 important distinctive features. Some of these will be hereafter 

 referred to. 



