PHYLOGENY OF THE PAL^EOGNATH^E AND NEOGNATILE. 221 



this region of the sternal plate is much thickened to form a prominent lip, looking 

 upwards. The coracoid grooves are exceedingly shallow and only just visible. As in 

 Apteryx, these grooves lie far apart, at the antero-lateral angle of the sternal plate. 

 The anterior lateral processes are short ; the articular surfaces for the sternal ribs lie 

 crowded together immediately behind the anterior lateral process, as in Rhea. The 

 posterior lateral processes are of great length ; the metasternum is often of great 

 length. The form of this and of the posterior lateral processes varies much in the 

 different groups into which the Dinomitb.es are divided. The length of the meta- 

 sternum in Apteryx does not extend beyond the posterior lateral processes. 



In jEpyornis the sternum resembles that of Apteryx more nearly than any other 

 Palceognathoe. As in Apteryx, the anterior border of the sternal plate is deeply 

 notched, the coracoid grooves are widely separated and very similar in form. The rib- 

 facets are wide and well spaced along the lateral border as in Apteryx, not crowded 

 together as in Shea or Dinornis. There are short but well-marked posterior lateral 

 processes, but there is no metasternal element. As Andrews has pointed out in a 

 recent and admirable paper on the skeleton of this bird, the sternum of JEpyornis 

 represents an embryonic stage. 



As Mr. Andrews has pointed out [4], the " sternum of JEpyomis 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 Eatitse." More especially does 

 this seem to apply, he goes on to point out, to the embryonic sternum of Apteryx. 



The sternum of the Crypturi differs from that of the flightless Palwognathce 

 chiefly in the possession of a large keel. In general form the corpus sterni recalls that 

 of Anomalopteryx. This is chiefly due to the large posterior lateral processes, which 

 in Crypturi arise very far forwards. The articular surfaces for the sternal ribs are 

 closely crowded and lie on either side of the coracoid grooves. The interarticular 

 spaces — incisurse intercostales — form deep pocket-like apertures, as in Dinornis and Rhea, 

 for instance. The crowding together and forward position of the articular surfaces for 

 the sternal ribs is another Rheine character. 



The anterior lateral processes are very similar in form and position to those of Rhea. 

 which they still further resemble in that the ventral aspect of the base lodges a 

 pneumatic aperture. 



The coracoid grooves in the Crypturi are separated by a deep gorge carved out of 

 the corpus sterni. These grooves differ from those of Rhea in that the upper and lower 

 lips are better developed, and in that their transverse extension is less while their depth 

 is greater relatively. 



There is a large spina interna. 



Turning once again to the corpus sterni and comparing that of Rhea macrorhyncha. 

 kindly lent me by Mr. Beddard, with that of a Tinamou. we notice a point of some 

 significance. To wit, that in Rhea on either side of the great median protuberantia 



vol. xv. — pakt v. No. 15. — December, 1900. 2 1 



