408 O. C. Marsh—Odontornithes, or Birds with Teeth. 
The geological horizon of all the Odontornithes now known is. 
the Upper Cretaceous. The associated vertebrate fossils are 
mainly Mosasauroid reptiles and Pterodactyls. 
A full description with plates of all the known Odontornithes 
is now being prepared by the writer. 
Yale College, New Haven, Oct. 18th, 1875. 
EXPLANATION OF PLATES. 
Plate IX.—Ichthyornis dispar Marsh. Twice natural size. 
igure 1. Left lower jaw; side view. 
Figure 2. Left lower jaw; top view. 
Figure 3. Cervical vertebra; side view: 
Figure 4, Same vertebra ; ait x 
Plate — regalis Mar: 
Figure 1. Left ‘gata jaw; side view; half natural size. 
Figure - Tooth; four times natural size. 
Figure 2. Left lower jaw; top view; half natural size. 
Figure 3. Dorsal vertebra; side view; natural size. 
Figure 4. Same vertebra; front view. 
