Enaliornis, England, vertebrae chiefly biconcave; Hesperornis, North America, vertebrae heterocoelous.
P. 344) a second fossil bird from the same locality was indicated as Ichthyornis dispar- from the fish-like, biconcave form of its vertebrae.
Pp. 403-408), to which were assigned as other characters vertebrae of a saddle-shape and not biconcave, a keelless sternum, and wings consisting only of the humerus.
On the other hand the Odontotormae, as exemplified in Ichthyornis, having the primitive biconcave vertebrae, yet possessed the highly specialized feature of teeth in distinct sockets.
- Biconcave, biconvex and concavo-convex (meniscus) lenses are employed in ophthalmic practice in the treatment of errors of refraction.
The cervical and thoracic vertebrae seem to be biconcave; the cervical ribs are much reduced and were apparently still movable; the thoracic ribs are devoid of uncinate processes.