Enough has already been said with regard to the position of the Order Ichthyornithes, with its sole Family ICHTHYORNITHIDAE; but it remains to discuss the several members. _Ichthyornis victor_, _I. dispar_, and the other species were small forms of about the size of a Partridge, with the habits and appearance, it is presumed, of Terns or Gulls.[48] The head was extremely large {49}in proportion to the remainder of the skeleton; the beak was long and pointed, with entirely separate rami to the mandible; the sharp teeth, fixed regularly in distinct sockets, were inclined backwards, and occupied the whole of the lower and at least the posterior half of the upper jaw; the keel of the sternum was large and broad; the dorsal and cervico-dorsal vertebrae were biconcave, as in _Archaeopteryx_, and perhaps to some extent in _Enaliornis_; the quadrate articulated to the skull by one knob, as in the Neornithes Ratitae and Neornithes Odontolcae; the metatarsus was short and the whole foot small; a furcula was probably present; the wings were well developed, indicating great powers of flight; while the tail was comparatively short, and ended in a pygostyle. It will be observed that of these characters the formation of the jaw and its teeth, the biconcave vertebrae, and the articulation of the quadrate, are those that chiefly distinguish the Order from the rest of the Carinatae. _Apatornis celer_, also from the Cretaceous deposits of Kansas, is probably to be placed here, but other genera described from the same strata cannot yet be certainly classified.[49] ORDER II. COLYMBIFORMES.