PHYLOGENY OF. THE PALJ£OGNATH,E AND NEOGNATH^E. 215 



In Rhea there are but seven free caudals. This is due to the great backward extension 

 of the ischia. Counting from the free end of the post-acetabular ilium backwards, as 

 in other forms, there are eleven post-iliac caudals. 



Ribs. 



The anterior cervical ribs (pleurosteites) have already been described. 



It is probable that the free cervical ribs (cervico-dorsal, Mivart) and the vertebra? 

 to which they articulate really belong to the thoracic series. This is indicated by the 

 fact that these ribs have lost their connection with the sternum, and have lost their 

 sternal ribs through the backward shifting of the sternal plate. 



In Casuarius and Dromwus there may be three or four free cervicals. In Struthio 

 and Rhea, two. In Apteryx one, which bears a large uncinate (in A. oiveni there is 

 a shorter and more style-like rib anterior to this and wanting the uncinate). 



In the Crypturi there are two free cervicals. 



The thoracic ribs in Casuarius and Drommus agree with Struthio, and differ from 

 Rhea, in the fewness and slight development of the uncinates. 



In Casuarius the 1st five pairs of thoracic ribs articulate with the sternum by means 

 of sternal ribs. The 6th and 7th are long, but have no sternal segments. The 7th 

 pair are more or less overlapped by the pre-ilium. The 8th pair are very short and 

 underlie the pre-ilium. The 9th pair are represented by a scale-like vestige repre- 

 senting little more than the tuberculum and capitulum, which in the young bird can 

 still be made out (e. g. 1374 a Mus. Coll.) closely applied to the pre-ilium. 



In C. bennetti there are but three free cervical ribs and only four pair of thoracic ribs 

 articulating with the sternum by means of sternal segments. The 5th pair have very 

 long sternal segments, but they fail to reach the sternum. We may gather from this, 

 however, that they have not long lost their connection therewith. 



The uncinates of the ribs of Casuarius are never large. Generally only two or three 

 appear to be present, and these may anchylose with their respective ribs. In a half- 

 grown C sahadorii I find five uncinates. These have been probably lost in maceration 

 in most of the skeletons which I have examined. 



In Drommus there are two free cervicals ; the second is very long, and almost 

 articulates with the anterior lateral process of the sternum. Following these come 

 four pairs of thoracic ribs connected with the sternum by sternal ribs. These are 

 succeeded by a pair (7th) with very long sternal segments, but which fail to reach the 

 sternum. The next two pairs have no sternal segments, and are overlapped by the 

 pre-ilium. 



In Struthio there are two free cervicals and five pairs of thoracic ribs articulating 

 with the sternum by means of sternal ribs. The pair next behind these has long 

 sternal segments which do not reach the sternum. In a mounted specimen in the 

 collection of S. camelus this 6th sternal segment actually articulates with the sternum. 



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