1874.] ANATOMY OF THE PARROTS. 589 



Lathamus, Psephotus, 



Nestor, Psittacus, 



Pionus, Psittacula, 



Platycercus, Pyrrhulopsis, 



Pyocephalus, Pyrrhura. 



It may be observed that the only other well-defined groups of 

 birds in which the carotids vary are the Cypselidae, Gallinse, Stru- 

 thiones, and Otididse. 



II. The presence or absence of the ambiens muscle. 



The ambiens muscle, the tendon of which crosses the front of the 

 knee-capsule obliquely from above downwards and outwards, and 

 ultimately forms part of the flexor perforans digitorum, is present in 

 the following genera — 



Ara, Nestor, 



Bolborhynchus, Pceocephalus, 



Ca'ica, Psittacus, 



Conurus, Stringops. 



It is absent in 



Agapornis, Licmetis, 



Aprosmictus, Loriculus, 



Brotogerys, Lorius, 



Cacatua, Melopsittacus, 



Calopsitta, Palceornis, 



Calyptorhynchus, Pionus, 



Chrysotis, Platycercus, 



Coracopsis, Prioniturus, 



Cyanorhamphus, Psephotus, 



Eclectus, Psittacula, 



Eolophus, Psittinus, 



Eos, Pyrrhulopsis, 



Euphema, Pyrrhura, 



Geopsittacus, Tanygnathus, 



Eathamus, Trichoglossus. 

 The only other well-defined groups of birds in which the ambiens 

 muscle is known to vary are the Columbse and the Struthiones. 



III. The presence or absence of the furcula. 



By this expression is meant the presence or absence of the furcula 

 as a complete bone ; for in those Parrots in which it is said to be 

 absent, the scapular ends of the two parts of which it is composed 

 are frequently to be found, being of considerable length in Stringops 

 and some of its allies. 



The furcula is complete in 



Aprosmictus, Brotogerys, 



Ara, Cacatua, 



Bolborhynchus, Ca'ica, 



