206 



Annals of the Carnegie Museum. 



enlarged. It grows gradually smaller, however, as we descend, being 

 of the least calibre in the lower third, when it again enlarges trans- 

 versely to support the trochleie for the digits. The upper half of the 

 bone is flat both posteriorly and at the lateral aspects. In front it is 

 longitudinally excavated down the middle, beginning where it is the 

 deepest, just below the inter-condyloid tubercle. As we gradually 

 pass to its lower half the shaft becomes subelliptical on section, the 

 major axis being transverse. 



At the base of the excavation above, a few millimeters below the 

 anterior crest of the summit, we find the shaft pierced by two foramina, 

 placed side by side. The innermost and larger one of these passes 

 rather obliquely through the bone to make its appearance, rather larger 

 in size, just inside of the hypotarsus. 



Considerably smaller, its companion pierces the tarso-martarsial 

 shaft, still more obliquely downwards, to make its exit as a foramen 

 of diminished calibre on the opposite side of the hypotarsus. The 

 posterior opening of this latter one is seen in Fig. 15. 



Fir,. 32. Left lateral view of the sternum of Nycticorax violaceiis (subadult). 

 Natural size, by the author from the skeleton of the same indivitlual that furnished 

 Figs. 28-30. 



Viewed from in front, the trochlene present the following points 

 for examination : the middle one extends the highest on the shaft, and 

 projects beyond the others anteriorly. It is distinctly grooved down 

 its middle, and descends the lowest. The inner one is the broadest 

 and is perfectly smooth in front, being but slightly grooved behind, 

 while the other two are decidedly so. Finally, the outer trochlea is 



