that connect the Orders and Families of Birds. 471 
niadæ as to confer the appellation of ** Piegrieches Hirondelles" 
upon one of the groups of this family. It gives an equal insight 
into the reasons why the Merulide and Sturnide should have been 
so closely united in the earlier systems, and some of their various 
groups so frequently confounded together; why, in particular, 
Linnæus should have placed in one and the same genus the Icteri, 
that belong to the Sturnide, and the Orioli, that come naturally 
among the Thrushes; and why, again, Pastor and Lamprotornis 
should so long have retained their station in the latter group. The 
same consideration still further points out the cause of the simila- 
rity between the Corvide and Psittacide in their relative perfec- 
tion of form and structure ; and explains why the family of Psit- 
tacidæ, though not the most perfect or typical with reference to its 
own tribe, as it yields to the Picide in this point of pre-eminence, 
is yet more perfect and typical than that family with reference to 
the character of the order, in consequence of its analogy to the 
Corvi. Many other similar coincidences and similar analogies 
will suggest themselves to the reader here, as well as in the in- 
ternal groups of the circles. 
There is another point of view in which the foregoing diagram 
is of service to the inquiries of the ornithologist. It points out 
the union of different groups with respect to characters not suffi- 
ciently essential, or too artificial to form the basis of a natural 
arrangement ; but which are yet important enough to force them- 
selves upon our notice, and which have, in fact, formed in many 
instances the foundation of well-received systems. On consult- 
ing the above table, we shall perceive that the principles, which I 
have endeavoured to illustrate, provide for due attention being 
paid even to such minor characters by the juxta-position of the 
groups in which they predominate ; and consequently, that the 
mode of grouping which these principles dictate, combines every 
advantage of artificial as well as of natural arrangement. Were 
we 
