44 
ON THE CLASSIFICATION OF BIRDS. 
eminently typical in their own circle, almost invariably 
present us with these variations in the form of their 
aberrant species. The restricted genus Parus is precisely 
of this description: it is the preeminent type of an entire 
subfamily; and hence, like Corvus, lAinius, Sylvia, 
and a great number of other genera, holding the same 
rank in their own circles, it contains a greater variety 
of modifications, in the form of its species, than genera 
which are not preeminently typical. The whole of 
the subgenera of Paras are distinguished from those of 
Sylvicola, by characters the most simple and beautiful. 
They all have that peculiar strength of foot so con- 
spicuous in our native examples, and 
their wings are invariably rounded; that 
is to say, the first quiU is short, and the 
second and tliird so graduated, that the 
fourth becomes the longest (^fig. 130. a). 
The bill also is short and thick, generally 
more or less conic, and sometimes (as in 
the types) very strong : the upper man- 
dible may be said to be entire, for in 
the only genus {Parisoma) which has 
the culmen arched, the notch is so small, 
that it may be termed obsolete. We are thus enabled 
to distinguish the whole from the neighbouring group 
we shall now enter upon. 
(47.) The second division of the titmice forms our 
genus Sylvicola. This extensive group possesses pe- 
culiar interest, inasmuch as it exhibits, after the most ' 
minute analysis, a demonstration of those general laws 
of classification, which we consider the foundation of 
the natural system, and by which, as we conceive, 
the whole creation has been regulated. Without, 
however, anticipating conclusions before we have de- 
tailed facts, it will he necessary to premise, that the 
whole of the birds whose natural arrangement we 
shall now consider, with the exception of one group, 
are natives of North America ; and that almost every 
fact we shall have occasion to mention, as illustrating 
their habits and economy, will be found recorded in the 
