Sternum, and Shoulder-Girdle 0/ iEpyornis. 385 



Edwards and Grandidier have already stated*, that we 

 find by far the closest resemblance to j^pyornis. The 

 two agree in the deeply concave anterior border, the 

 "widely separated and similarly situated coracoid grooves, 

 their great relative width, and the presence of four costal 

 facets. In the posterior region the likeness is not so great, 

 but in Apteryx this portion of the sternum is very variable 

 in form. Usually there are a pair of lateral processes and a 

 somewhat shorter median one, but the latter may be divided 

 by a median notch (as in some of the Dinornithidae), or 

 may, occasionally, be entirely wanting, in which case the 

 resemblance to the fossil is very great. This latter con- 

 dition is shown in the figure of the sternum of A. oweni 

 given in Meyer's 'Abbildungen von Vogel-Skeletten,' pi. 54. 

 In this case the lack of the median process probably results 

 from ossification not having extended into that portion of the 

 metasternal cartilage ; in jEpyortiis, on the other hand, this 

 cartilage appears never to have been developed, for, as above 

 mentioned, the middle of the posterior edge of the sternum 

 for about 2^ cm. is thin and sharp, and clearly was not 

 bordered by cartilage, although a fringe of that substance 

 extended on either side along the rest of the hinder margin. 

 If, therefore, as seems probable, the metasternal region is 

 wanting, the sternum of ^pyornis consists of the two 

 primitive costo-sternal elements only, and in this respect 

 corresponds to an embryonic stage in the development of the 

 sternum in the recent Ratitsef. 



The sternum of an embryo of Apteryx australis figured by 

 Prof. Jeffery Parker on pi. xvi. fig. 218 of his memoir " On 

 the Structure and Development of the Apter7/x " (Phil. Trans, 

 vol. 182 (1891) B) shows this condition, the metasternal 

 region being still entirely absent; and if ossification had taken 

 place at this stage without the further addition of cartilage, 

 the resulting sternum would be almost exactly equivalent to 



* " Observations sur les JEpyornis de Madagascar," Comptes Rendus 

 Acad. Sci. vol. cxviii. (1894) p. 125. 



t See Lindsay, "On the Avian Sternum," Proc. Zool. Soc. 1885, 

 p. 711. 



