ON THE SYSTEMATIC POSITION OF HESPERORNIS. 5 
The posterior end only of the pterygoid bone is figured by Marsu, but this 
small portion is of great interest, for it shows besides the socket for the pterygoid 
_ process of the quadrate bone, another distinct, lateral, articular surface. Now the 
pterygo-quadrate articulation is remarkable in the Divers: for the pterygoid articu- 
lates with the quadrate not only by its head, but again a little way in front by its 
external surface, which comes in contact with the anterior process of the quadrate. 
This condition occurs to some extent in certain other Schizognathous birds, for 
instance the Fowls, but is quite absent in the Grebes. It is therefore one of the 
points in which we consider that Hesperornis resembles the Colymbidze more 
definitely than the Podicipide. 
Thus, in short, it appears to us that in the three most crucial regions of the 
skull where resemblances to Ratite characters have been sought, these resemblances 
break down ; but that in all three the real resemblances are with the Colymbide. 
Passing to the other regions of the skull, the general shape, the narrow orbital 
“waist,” the distinct sagittal and occipital crests, are quite similar in Colymbus and 
Hesperornis. The glandular supra-orbital depressions, so characteristic of the 
Colymbidze as well as of the Alcidee and Laride though nearly obsolete in the 
Grebes, are present in Hesperornis. None of these are Struthious characters. The 
inter-orbital fenestra, very small in the Ratites as in the Fowls, is here very large, 
as in Colymbus, though not so enormous as in Podiceps. 
The nostrils are holorhinal, and the nasal bone is identical in form with that of 
Colymbus: in the Ratites it is as different as can be, for its external process is © 
wanting altogether.* 
The lachrymal bone of Hesperornis is imperfectly defined in Marsn’s figure, 
but, if I understand it aright, it is by no means unlike that of Colymbus, and 
certainly very different from the large, flat, curved bone in the Ratite. 
The description given of the premaxillariest is not very diagnostic, but the 
two chief points noted, the posterior longitudinal fissure and the lateral excavation, 
are to be found in the Grebe and the Diver, but are distinctly not present in the 
Ratitee. 
The posterior view of the skull is very much like that of Colymbus, for example 
in the form of the foramen magnum, the cordate shape, large size, and great 
prominence of the occipital condyle, and in the characters of the ex-occipital region 
which does not form the broad descending process characteristic of the Ratites. 
The great descending process of the squamosal, which in the Ratites overlaps 
the head and body of the quadrate, is entirely absent in Hesperornis. 
* Cf. Garrop. Collected Papers, p. 129. 
t“ The premaxillaries are elongate and separate throughout their posterior two-thirds. Their extremities 
touched the frontals. Their sides are deeply excavated for the anterior nares, and in front they are 
ankylosed, and form a long pointed beak, the end of which is somewhat decurved.” (Marsu, loc. cit., p. 8.) 
