CHAP, in 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 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 Arcliae- 

 opteryx, and perhaps to some extent in Enaliornis ; the quadrate 

 articulated to the skull by one knob, as in the Neornithes Eatitae 

 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. 1 



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 COLYMBI 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, Coim. 1880. 

 VOL. IX E 



