SUPER-ORDER III DROMAEOGNATHAE 269 



and the weight of the body carried mainly by the third, a high degree of 

 specialisation due to modification for running. Fossil remains of these birds 

 occur in the Lower Pliocene of the Siwalik Hills and the Island of Sainos, 

 while fossil eggs, slightly larger than those of the living ostrich, have been 

 described under the name of Struthiolithus, from superficial deposits of Southern 

 Russia and Northern China. This would seem to indicate that the range of 

 the group has been restricted through the agency of man. 



Family 2. Rheidae. 



The rheas have the ischia turned inward, so that they meet and are united 

 beneath the ilia, while a number of the anterior caudal vertebrae are crowded 

 out and aborted : they have three digits in the foot. The species of this 

 family are confined to southern South America, where remains referable to 

 existing species occur in Pleistocene deposits. 



Diatryma, Cope, from the Eocene of New Mexico, was assigned to this group 

 by Cope, but it is very doubtful if this is correct ; the affinities of Diatryma 

 appear to be rather with the South American PhororJiacidae. 



Family 3. Dromaiidae. 



The emeus from Australia, and the cassowaries from Northern Australia, 

 and a number of the islands to the northward, have no striking peculiarities 

 of the pelvic region, and are three-toed. The bones of the wing are very 

 greatly reduced in size. Allied to the emeus is Genyoniis from the Pleistocene 

 of Australia, a bird of massive build with a skull 0"3 m. in length. Hypselornis 

 occurs in the Pliocene of India. 



Family 4. Aepyornithidae.^ 



The Aepyoriiitludae, although known only by fossil remains, including entire 

 egg-shells, from Northern Madagascar, have become extinct at a comparatively 

 recent epoch. They were birds of great size and massive build, having a 

 relatively small skull and an unusually short and broad sternum, with well- 

 developed facettes for the coracoids. Foot normally with four digits, but the 

 hallux is sometimes wanting. The nearest relatives of these birds are con- 

 sidered to be the cassowaries and emeus. The typical species is the 

 unfortunately named Aepyornis maximus, a species considerably exceeded in 

 size by A. titan, which has a tibia 80 cm. in length. 



Family 5. Dinornithidae. 



The Dinornithidae ^ comj^rise about twenty or twenty-five species of birds 

 popularly known as Moas. 



1 Andreios, C. W., Skeleton of Aepyornis (Ibis, p. 376), 1896. Also, Geol. Mag. [4], vol. IV. 

 (1897), p. 241. — Bicmconi, G. G., Recherches sur I'Epyoruis maximus (Ann. Sci. Nat. Zool. [5], vol. 

 HI. p. 58), 1865. — Capellini, G., Sul primo novo di Aepyornis maximus arrivato in Italia (Mem. Acad. 

 Sci. 1st. Bologna [4], vol. X.), 1889. — Milne-Edwards, A., and Gra/iuUdier, A., Ann. Sci. Nat. Zool. 

 [5], vol. XII. p. 167), 1870. 



- For fiapers relating to Dinornithidae, see Hamilton, A., Bibliography of Dinornithidae (Trans. 

 New Zeal. Inst. XXVI. (1893), p. 229). Also, Button, F. W., New Zeal. Jouni. Sci., Nov. 1891, 

 p. 6. — Po/rker, T. J., On the Cranial Osteology, etc. of Dinornithidae (Trans. Zool. Soc, London^ 

 vol. XIII. p. 373), ii^b.— Andrews, C. W., Skeleton of Megalapteryx (Novit. Zoologicae, vol. 11. 

 p. 188), 1887. 



