270 Mr. Vicors’s and Dr. Honsrrgrp's Description of the 
nearly an equal length and similar construction to that of the 
true Psittacus*, which immediately. precedes the present sub- 
family. While Calyptorhynchus is allied to the Maccaws in the 
characters of this member, and thus evinces a higher develope- 
ment than Plyctolophus of the typical peculiarities of the family. 
The culmen of the upper mandible is considerably curved and 
bent inwards at the aper ; in some species when viewed in pro- 
file it has a semilunar appearance. The under mandible is 
much more dilated also than it is in Plyctolophus, In most 
specimens which we have seen of this genus the shafts of the 
tail-feathers are prolonged beyond the webs; a peculiarity 
which seems to indicate something distinctive in the economy of 
the birds. From all the accounts we have received of them they 
seem much less gregarious than the birds of the conterminous 
genus. The group appears to be confined to Australia. The 
black colour that prevails through these birds separates them 
also at first sight from the species of Plyctolophus, which are 
generally white. The species of the latter genus, which has 
been just enumerated in our catalogue, P/. Eos, and the Caly- 
ptorhynchus galeatus, which will be presently noticed, both of 
.* The group of the Psittacide, to which the name of Psittacus should be applied, 
may perhaps be considered to be that which comprises the Psitt. Amazonicus, Briss., 
and some allied species. "That at least is.the group best known under the old scientific 
term, and at the same time under the familiar names of Parrot in our language, and 
Perroquet in the French, which correspond with it. In general, when we subdivide 
a group, we ought to retain the original name for that subdivision of it which contains 
the typical species. "There are instances, however, where this mode cannot well be fol- 
lowed, as when the typical species have already been distinguished by generic names. 
This happens to be the case in the group before us, the typical species of which were 
the first that were separated by distinct names. These have long been called Macro- 
cercus and Plyctolophus, or more familiarly Maccaws and Cockatoos; and we cannot 
venture to disturb these established names, even for the sake of scientific correctness. 
The most eligible rule, next to that of selecting the typical species for the original name, 
is probably that of selecting the species to which it has been most familiarly applied. 
which 
