APPENDIX. 
On a New Sub-class of Fossil Birds (Odontornithes) ; 
by O. C. Marsa. 
THE remarkable extinct birds with biconcave vertebrae 
(Ichthyornidae), recently described by the writer from the 
upper Cretaceous shale of Kansas,* prove on further investiga- 
tion to possess some additional characters, which separate them 
still more widely from all known recent and fossil forms. The 
type species of’ this group, Ichthyornis dispar Marsh, has well 
eveloped teeth in both jaws, These teeth were quite numerous, 
and implanted in distinct sockets. They are small, compressed 
and pointed, and all of those Bien are similar. Those in 
the lower jaws number about twenty in each ramus, and are all 
more or less inclined backward. "The series extends over the 
entire upper margin of the dentary bone, the front tooth being 
very near the extremity. The maxillary teeth appear to have 
been equally numerous, and essentially the same as those in the 
mandible. 
The skull is of moderate size, and the eyes were placed 
well forward. The lower jaws are long and slender, and the 
hot encased in a horny s : 
The scapular arch, and the bones of the wings and legs, all 
conform closely to the true ornithic type. The sternum has a 
united, as in ordinary birds. The bones of the posterior extrem- 
ies resemble those in swimming birds. The vertebre are 
*This Journal, vol. iv, p. 344, Oct. 1872, and vol. v, p. 74, Jan., 1873. 
