CHAP. 11 COLYMBIFORMES 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 m 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 Archae- 
opteryx, and perhaps to some extent in Lnaliornis ; the quadrate 
articulated to the skull by one knob, as in the Neornithes Ratitae 
and Neornithes Odontoleae; 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.' 
Order II. COLYMBIFORMES. 
The Colymbiformes constitute a very archaic Order of Birds, 
and hold a somewhat isolated position. Older writers combined 
them with the Alcidae as a group Pygopodes, but recent anatomi- 
cal investigations make it clear that Auks have more affinity to 
Gulls, which again trend to the Limicoline alliance. As regards 
structure, the two Sub-Orders CoLymBiI and PODICIPEDES, with 
their Families Colymbidae, or Divers, and Podicipedidae, or Grebes, 
may be here treated together. They are all water-birds with 
webbed or lobed toes and extraordinarily flattened metatarsi. 
The sternum in the Colymbidae is much longer than broad, in the 
Podicipedidae short and wide, while the furcula is Y-shaped; the 
neck is more or less elongated; the bill in the former Family is 
strong, straight, acute, and compressed, in the latter moderate and 
sometimes recurved, being either slender, as in Aechmophorus, or 
very stout, as in Podilymbus. The scutellated metatarsi are set 
very far back, and are fairly long, the procnemial process of the 
tibia being remarkably elongated, though Grebes alone have a 
distinct patella; the hallux is very small and has a small mem- 
1 For these refer to Prof. Marsh’s Odontornithes, New Haven, Conn. 1880. 
VOL. IX EK 
