588 MR. A. H.GARROD ON THE [Nov. 3, 



The points to which my attention has been directed, on account 

 of the variations observed, are : — 



1 . The arrangement of the carotid arteries ; 



2. The presence or absence of the ambiens muscle ; 



3. The presence or absence of the furcula ; 



4 . The presence or absence of the oil-gland ; 



and others of minor importance, such as the complete encirclement 

 of the orbit by bone, and the peculiarities of the atlas vertebra. 

 These will be considered separately. 



I. The arrangement of the carotid arteries among the Parrots. 



In my paper on the carotid arteries of birds, the peculiarities of 

 these vessels in the Parrots are described, it being shown that three 

 different, arrangements of these vessels obtain, and perhaps a fourth. 

 Either the two carotids may run normally, independent, and side by 

 side up the front of the neck, in the hypapophysial canal ; or the 

 right, as usual, traverses that canal, whilst the left runs superficially 

 along the sjde of the neck in company with the left pneumogastric 

 nerve and the jugular vein ; or the left carotid may alone be developed, 

 as in the Passeres and many other birds. It has been stated that 

 Meckel found a fourth arrangement in Cacatua sulphurea ; but in a 

 specimen of that species recently dissected by me, the left only was 

 present, as in C. cristata, C. leadbeateri, and C. galerita. 



To make this paper complete in itself, and to incorporate those 

 dissections performed since the other was published, a list of all the 

 Parrots which I have examined, together with the condition observed 

 in them is given. 



1 . The two carotids are present, running normally, side by side, in 



Agupornis, Loricidus, 



Aprosmictus, Lorius, 



Calopsitta, Melopsittacus, 



Calyptorhynchus, Palcenrnis, 



Eclectus, Prioniturus, 



Eolophus, Psittinus, 



Eos. Stringops, 



Euphema, Tanygnathus, 



Geopsittacus, Trichoglossus. 

 Licmetis, 



2. The left carotid only is present in 



Cacatua. 



3. The two carotids are present, the right having its normal 

 course, the left running superficially along with the left pneumogas- 

 tric nerve in 



Ara, Chrysotis, 



Bolborhynchus, Conurus, 



Brotogerys, Coracopsis, 



Gaica, Cyanorhamphus, 



