RATITjE. 241 



Sub-Order 7. Struthiones. 



The only Ratite birds whose range at the present day 

 extends to the northern hemisphere are the Ostriches or 

 STRUTHIONES. They are represented by a single genus, 

 Struthio, in Africa and Arabia; but a two-toed bird not yet 

 generically distinguished from this occurs in the Lower Pliocene 

 of the Siwalik Hills, India, and in that of the Island of Samos, 

 in the Turkish archipelago. 



INCERT.E SEDIS. 



There is some reason to believe that other Ratites, of an 

 extinct primitive type, ranged into the northern hemisphere 

 both in Europe and in America during the early Tertiary 

 period. Gastornis, at least, from the Lower Eocene of western 

 Europe, is generally regarded as a bird of this kind, with the 

 pectoral arch less modified than that of the later genera. 

 Dasornis may have been another Ratite, but is only known by 

 one imperfect cranium from the London Clay of Sheppey; 

 while Diatryma, represented by a tarso-metatarsus from the 

 Eocene of New Mexico, may represent the order in North 

 America. 



Gastornis. The best-known species of this genus (G. edwardsi) is re- 

 presented by fragments of the head, cervical and caudal vertebrae, portions 

 of ribs, the furcula, coracoid, humerus, radius, metacarpus, ischium, 

 pubis, femur, tibia, tarso-metatarsus, and phalanges. The skull is rela- 

 tively large, and the sutures between its elements are unusually per- 

 sistent. The premaxillse bear a pair of rounded bosses of bone, each of 

 which may possibly have supported a tooth, though this remains un- 

 certain. The mandible exhibits a conspicuous post-articular process. 

 The caudal vertebra) are small and cannot have borne more than a very 

 small pygostyle. The clavicles are fused into a furcula, and the cora- 

 coids are much more slender than usual in the Ratitae. The sternum is 

 known only by fragments of the lateral margin. The humerus is large 

 and with well-formed distal condyles ; the elements of the metacarpus do 

 not appear to have been fused together. The pelvis seems to have had 

 a relatively short postacetabular portion ; and the distal end of the 

 ischium is expanded upwards towards the hinder portion of the ilium. 

 The great trochanter of the femur does not rise above the level of its 

 head. The tibio-tarsus exhibits a bony bridge over the groove for the 

 extensor tendons. The tarso-metatarsus is long and slender, with the 



w. 16 



