PROCEEDINGS OF THE NATIONAL MUSEUM. 



341 



term is allowable) in the development of the sacral parapohyses in the 

 various species. 



Fia. 4. — Composite sacrum of Par us carolinensis, the right and left halves being from two individuals. 

 Enlarged. The diftVrenoe between the last two presacrals of either side should be noted, as well as 

 the fact that there is one more parapophysis on the left half of the figure than on the right. 



The species in hand have each six free candals and a pygostyle, with 

 the exception of ^EgithaluSj which has seven candals and a pygostyle. 



The fore and hind limbs are respectively made on the same plan 

 througfibut the group, and there is little to be said regarding them. 



The following table shows tlie pneumatic or non-pneumatic condition 

 of the sternum and humerus in the various species examined, the two 

 species of Polioptila being introduced to show that variation in this 

 resi)ect may occur in closely related species. 



The columns headed above and below denote that the pneumatic fo- 

 ramina are respectively above or below the septum dividing the pneu- 

 matic fossa, and in two cases it will be seen that foramina exist on both 

 sides of the septum, the opening above being much the larger. 



This table shows that the larger Titmice usually, although not al- 

 ways, have a pneumatic sternum and humerus, while in the smaller 

 species these bones are non-pneumatic. It also shows that, while a 

 pneumatic sternum is usually correlated with a pneumatic humerus and 



