Shufeldt : Osteology ok the Psitiaci. 411 



The sixth vertebra loses the neural and hypapophysial s|)ines al- 

 together ; the para[)Oj)hyses graduall)- diminish in size from this seg- 

 ment down the » hain, until they, with the pleurapophyses, again be- 

 come prominent as tVee ribs. Likewise the neural and lateral canals, 

 which are here ([uite small, also increase in calibre as we proceed in 

 the same direction. This vertebra has also a short carotid canal present 

 in j)lace of the hyjiapophysis. And this last feature is still better 

 marked in the seventh vertebra, though it remains open below. These 

 are the only two which have it in this parrot, in the eighth its site 

 being again occupied by a low, median, hypapophysial spine. 



In all these segments, as well as in the few succeeding ones that we 

 fnul before coming to the true dorsals, the pre- and postzygapophyses 

 are diverging limbs of the most usual form in .-l7'rs. The articulation 

 among the centra is heteroccelous. 



The ninth vertebra has the neural spine commencing to make its 

 appearance again, and is here a low tubercle, more prominent in the 

 tenth, and thus on till it assumes the dorsal form of this spine. l"he 

 hypapophysial plates in both the ninth and tenth vertebrae are deep, 

 long, and of a quadrate form, and from the lateral masses being low 

 on the sides of the centra, they appear sunken between these pro- 

 tuberances. 



We find that the twelfth vertebra has much the general aspect of 

 one of the dorsals, and, moreover, its pleurapophyses have become 

 freed as a tiny pair of ribs. These attain quite a respectable length in 

 the thirteenth vertebrae, while in the fourteenth, where they are still 

 unconnected with the sternum, they possess small unciform processes. 

 This practically agrees with w'hat w^e find in Cacatiia. (PI. II, Fig. 8.) 



We may term the fifteenth to the eighteenth vertebrae inclusive true 

 dorsals, for they all have ribs connecting them in the usual way with 

 the sternum. They also have interlocking neural s])ines, and their 

 transverse processes are strengthened by each one developing a single 

 spiculiform interlacing metapophysis at its outer extremity. Prominent 

 hypapophyses are found upon the thirteenth, fourteenth, fifteenth, and 

 sixteenth, and a small one sometimes on the seventeenth vertebra. 



The ribs have broad unciform processes anchylosed to them, but 

 there are still two other pairs that come from beneath the pelvis, be- 

 longing as they do to the sacrum, that also meet costal ribs below, 

 which do not have these appendages. 



Sometimes abortive ribs are found anchylosed to the twenty-first and 



