ee ON THE SYSTEMATIC POSITION OF HESPERORNIS. 
Fig. 16. Patetta or HESPERORNIS. 
which, small and double in the Ostrich, is rudimentary or absent altogether 
in the other Ratites, is of immense size and peculiar shape in Hesper- ' 
ornis. In this bird it is a long trihedral pyramid, pointed at its superior 
extremity, concave on its outer surface, bearing at its lower extremity special and 
separate articular surfaces for the tibia and femur, and lying in a line with the long 
axis of the femur. Except that it is perforated for the tendon of the ambiens 
muscle (as in the Gannet), it is extremely like the patella of the Grebe, and 
practically identical with that of Colymbus, except that in this latter it is fused 
with the upper extremity of the tibia. The existence of a small additional sesamoid 
oye 
aro Sli 
La Oo nn Eo 
Legs 
Be ee se 
fig. 17. Lerr Trpta, with co-ossiriep Parrnia or CoLyMBus. 
in the knee-joint of Colymbus (OWnn, Comp. Anat., iL, p- 838) does not invalidate 
the homology here adopted of the long “rotular process of the tibia” with the 
patella. 
The resemblances and differences on which the whole preceding argument is 
based may be small points if taken separately, but the strength of the case must 
rest on their great number, and on their all, without exception, pointing the same 
way. Many of the points are not easily made clear with the means of illustration 
at our command. Such as they are, they may be recapitulated as follows :— 
In the skull of Hesperornis 
The sagittal and occipital crests are present as in Colymbus: but they 
are quite absent in the Ratites. 
The supra-orbital glandular depressions are present as in Colymbus: but 
they are quite absent in the Ratites. 
