268 AVES CLASS iv 



Super-Order 3. DROMAEOGNATHAE/ 



The skull is of the Dromaeognathous type, and the head of the quadrate 

 is Single, save in the Apteryges, in which the articular head is broad, and 

 almost, or quite, double. While the single-headed quadrate is also found in 

 the toothed birds Ichthyornis and Hesperornis, in these the halves of the lower 

 mandible are free from one another, a point wherein they difFer from other 

 birds. The ischia are never united with the ilia save at the extreme distal 

 portion, and are usually slender and free, while the aspect of the entire pelvis 

 is quite Hifferent from that of the Euornithes. The upper end of the tarsus 

 is never perforated for the passage of tendons, and the terminal caudals do not 

 fuse to form a pygostyle. 



The Dromaeognathae comprise a small number of birds difFering from one 

 another in important particulars, but all evidently related to, or directly 

 descended from, old and primitive forms ; they may be considered as the 

 scattered survivors of the ancient avi-fauna of the globe, and some are confined 

 to a remarkably small area. It is scarcely too much to say that greater 

 differences of structure are to be found among the few members of this division 

 than among all other existing birds, and these differences are such that they 

 are frequently placed in different Orders. The flightless struthious birds have 

 a sternum devoid of a keel, and very variable in shape posteriorly, while the 

 Shoulder girdle exhibits various degrees of degeneration from the absence of 

 cla vieles to the lack of the entire wing. The pelvic region is also very variable 

 as to the ischia and pubes. 



Order 1 STRUTHIONBS. 



This Order comprises the true ostriches (Struthio), the rheas (FJiea), the 

 cassowaries, and emeus (Casuarius and Dromaius), these forming three groups 

 in the order given, which are sometimes raised to ordinal rank, but more often 

 considered as families, super-families, or sub-orders. The extinct Moas forming 

 the family Dinornithidae form a distinct division, and the Aepyornithes of 

 Madagascar still another, although owing to lack of knowledge of their palatal 

 structure these last cannot be accurately placed. 



These are all large flightless birds, having, so far as known, a typically 

 Dromaeognathous skull with the long basipterygoid processes arising from the 

 body of the parasphenoid, giving it something of a cruciform shape ; the 

 nostrils are holorhinal. The sternum is not keeled ; the scapula and coracoid 

 are short and fused with one another, and the wings small. All these, how- 

 ever, are negative characters correlated with loss of the power of flight. 



Family 1. Struthionidae. 



In the Struthionidae, or ostriches, the pubes are united in a ventral Sym- 

 physis, the toes reduced to two, the third and fourth digits only being present, 



^ PycrafU W. P., Morpliology and Phylogeny of the Palaeognathae [Ratitae and Onjiitvn) and 

 Neognathae {Carinatae), (Trans. Zool. Soc, London, vol. XV. p. 149), 1900. This important paper 

 contains a very füll bibliography of works relating to the group here called Dromaeognatlwe. Mr. 

 Pycraft shows very clearly that the groups Ratitae and Carinatae are artificial. and that the 

 Tinamous belong with the Ostriches. 



