ON THE ANATOMY OF THE PARROTS. 255 
Genera in which the left carotid Genera in which the left carotid 
has remained normal. has become superficial. 
(PALZORNITHIDZ) (PsITTAcIDz2.) 
Geopsittacus. Nestor. 
Loriculus. Pionus. 
Lorius. Platycercus. 
Melopsittacus. -  Peeocephalus. 
Paleornis. Psephotus. 
Prioniturus. Psitiacus. 
Psittinus. Psitiacula. 
Stringops. Pyrrhulopsis. 
Tanygnathus. Pyrrhura. 
Trichoglossus. 
Each of these secondary types must have then become a centre for 
variation in itself. From the 4th combination, in which only the 
carotids are peculiar, sprang the 5th, 6th, and 7th, with the ambiens 
deficient, just in the same way that the 1st, 2nd, and 3rd combinations 
originated from the ancestral form by the same process of reduction. 
The loss of the furcula and of the oil-gland (though never, as it Page 594. 
happens, both together) have further aided in the formation of tertiary 
and further subdivisions, which, upon the dissections above given, 
would lead to the arrangement of the family which is depicted in 
Plate LXX [6.]. 
This may be represented in the tabular form as follows :— 
Suborder (or Cohort) PSITTACI. 
Family I. Panzornituipz. (Left carotid normal.) 
The ambiens muscle absent. Carotids two, except in the genus 
Cacatua. 
Subfamily (1) Panzorxiramnz. No further deviation. 
Paleornis. 
Eclectus. 
Aprosmictus. 
Tanygnathus. 
Prioniturus. 
Psittinus. 
Loriculus. 
Trichoglossus. 
Lorius. 
Eos. 
Subfamily (2) Cacarurnz. Orbital ring completely ossified, 
and characteristic in that it develops a process bridging 
the temporal fossa (vide Plate LXXI [7.]). 
