THE QUADRATE BONE IN BIRDS. 13 
broad, and truncated. The pterygoid condyle is elevated in an exceptional degree. 
The deep ovoid quadrato-jugal cup is placed at the postero-inferior angle. The 
mandibular articular surface is normal, lacking the accessory trochlea. 
The quadrate of the Tern very closely resembles that of the Gull in all essential 
Fig. 24. STERNA HIRUNDO. 
features. The quadrato-jugal cup is singularly small. 
In the Razorbill the capitula are small and deeply separate. The shaft of the 
bone is slender, and the anterior process of moderate size. The quadrato-jugal cup 
fig. 25. Aca TORDA. 
is deep, and situated postero-inferiorly. The pterygoid condyle is much raised. 
The mandibular articulation is of the normal pattern. 
We have examined, by Dr TRaquair’s permission, the quadrate of a Great 
Auk’s skeleton, recently acquired for the Museum of Science and Art, Edinburgh. 
It corresponds with the Razorbill’s very exactly, the only difference perceptible 
being that the mandibular condyles are rather more massive. 
From the foregoing description and figures, it is plain that the quadrates of the 
Gull and the Razorbill are, comparatively speaking, alike, and that in a less degree 
the Petrel and the Grebe resemble one another. 
The Gull and the Razorbill agree in the deeply-cleft capitula, the blunt square 
anterior process, the high pterygoid condyle, and the absence of the accessory 
trochlea. 
The Petrel and the Grebe differ indeed in general form, but possess in the 
accessory trochlea a common feature. 
There are not wanting other characters, as, for instance, Nirzscu’s ptery- 
lographic figures will show, to corroborate this alliance of the Procellariidee and 
Colymbidze on the one hand, and of the Laridz and Alcide on the other. A close 
alliance between the Gulls and the Grebes, as suggested by Huxtey (la. cit., 
p. 458), is not borne out at any rate by the quadrate bone. 
