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108 ORNITHOLOGY AND OOLOGY. 
ORDER III.—INSESSORES. Perrcuers. 
In accordance with the views of many systematic writers, 
it may perhaps be as well to retain an order Jnsessores, 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 Jnsessores 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 Jnsessores, constituting 
important distinctive features. Some of these will be hereafter 
referred to. 
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