Page 593. 
254 ON THE ANATOMY OF THE PARROTS. 
two carotids, running symmetrically in front of the neck, and that the 
ambiens muscle was present, as was the furcula and the tufted oil- 
gland. The intestinal ceca and gall-bladder must have been absent or 
lost very early, as must the postacetabular portion of the tensor fascize 
muscle ;* for they are none of them to be found in any existing 
species; whilst the beak, tongue, crop, and rectrices must have 
possessed the characteristic features, which are not found to vary to 
any important extent. The pterylosis of the suborder forms a con- 
siderable but much involved field for work, which has only been 
entered upon by the illustrious Nitzsch. 
Referring back to the characterising features of the existing species 
whose internal structure has been noted, it will be seen that none has 
as yet been found with a conformation exactly similar to that of the 
above-described ancestral bird ; in other words, no existing Parrot has 
been seen with two normal carotids, an ambiens muscle, a furcula, and 
an oil-gland. By more than a single way, however, this condition, 
with only one exceptional character, is found to exist. For instance, 
the fourth combination above given, in which the ambiens, furcula, 
and oil-gland are present at the same time that the carotids are 
abnormal (the left being superficial), agrees with the type except in 
one point—the disposition of the carotid arteries. Again, in the first 
of the combinations the only deviation from the type consists in the 
absence of the ambiens muscle. 
These two different directions of variation must therefore have 
formed the secondary stems from which the more specialized genera 
subsequently sprang. In other words, the main stem must have given 
rise to two, in one of which the carotids remained normal, whilst in 
the other the left became superficial. The following are the genera 
as they will thus appear :— 
Genera in which the left carotid Genera in which the left carotid 
has remained normal. has become superficial. 
(PALHORNITHIDZ. ) (PsI?TaciDzZ. ) 
Agapornis. Ara. 
Aprosmictus. Bolborhynchus. 
Cacatua. Brotogerys. 
Calopsitta. Caica. 
Calyptorhynchus. Chrysotis. 
Eclectus. Conurus. 
Eolophus. Ooracopsis. 
Eos. Oyanorhamphus. 
EHuphema. Lathamus. 
* Vide “ Proceedings of the Zoological Society,” 1873, p. 628. (Supra, p. 189.) 
a 
OO OO ———— 
