PHYLOGENY OF THE PALZOGNATHZ AND NEOGNATHA, 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. 
Riss. 
The anterior cervical ribs (pleurosteites) have already been described. 
It is probable that the free cervical ribs (cervico-dorsal, Mivart) and the vertebrae 
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. owent 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 Dromeus 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 Caswarius are never large. Generally only two or three 
appear to be present, and these may anchylose with their respective ribs. In a half- 
grown © salvadorii I find five uncinates. These have been probably lost in maceration 
in most of the skeletons which I have examined. 
In Dromeus 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. Ina mounted specimen in the 
collection of S. camelus this 6th sternal segment actually articulates with the sternum. 
2H2 
