ON THE SYSTEMATIC POSITION OF HESPERORNIS. iL 
Fig. 6. AXIS VERTEBRA OF COLYMBUS. 
no lateral perforations; in Colymbus a thin, sharp hemal spine runs downwards 
from the posterior half of the body of the vertebra, and the existence of this in a 
precisely similar position is indicated in Marsu’s figures of Hesperornis. 
The figures given above show how closely, in every detail of form, for instance in 
the notches above the posterior extremity of the vertebral body, in the ridge 
proceeding to the posterior zygaphysis, and in the character of the odontoid process, 
the two vertebree agree. 
The third vertebree resemble one another in the two birds in great detail, 
except that the neural spine is absent, or possibly not preserved, in Hesperornis. 
fig. 8. THIRD CERVICAT, VERTEBRA OF COLYMBUS. 
The great tubercles over the posterior zygapophysis (hyperapophyses, Mrvart) are ° 
striking points of resemblance, and are wanting or rudimentary in the Ratites, and 
the posterior zygapophyses are set at the sides of the neural canal instead of above it 
as in the Ratites. ‘The middle part of the vertebral body is much compressed from 
side to side, while it is broad and oblong in the Ratitee. 
