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Show 588 MR. A. H. GARROD ON THE [NOV. 3, The points to which m y 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 m y 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 side 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 Agapornis, Loriculus, Aprosmictus, Lorius, Calopsitta, Melopsittacus, Calyptorhynchus, Palaornis, Eclectus, Prioniturus, Eolophus, Psittinus, Eos. String ops, 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 pneumogastric nerve in Ara, Chrysotis, Bolborhynchus, Conurus, Erotogerys, Coracopsis, Ca'ica, Cyanorhamphus, |
