176 Annals of the Carnegie Museum. 



In the Great Blue Heroii (a bird that I have alhided to several times 

 above as simply the Blue Heron) the outer border of either ramus of 

 the mandible for nearly two-thirds of the distance back from the apex 

 is very sharp, and along the middle third of the entire length of the 

 bone, it is swelled just within this cutting edge, which enlargement 

 has its mesial boundary developed also as a sharp border, parallel to, 

 but on a lower plane with, the outer ramal edge. 



The inferior ramal borders are rounded for their entire lengths, 

 merging into the gently upward curved symphysial extremity anteri- 

 orly, to l)e extended behind to the very ends of the articular parts, 

 while on each side they curve towards the median plane. On the 

 external aspect of a ramus we see numerous minute foramina arranged 

 roughly in two longitudinal rows. Some venated markings are also 

 present. No ramal fenestra pierces this bone, where it occurs in many 

 other birds ; but an oblique split plainly marks the site where it was 

 sealed over during the development of the mandibular elements. This 

 entire external surface is smooth and liat, becoming gently convex 

 only as it sweeps beneath the articular ends behind. As I have said, 

 the posterior third of the superior ramal border is somewhat flattened 

 with rounded inner and outer margins. To the rear of the middle of 

 this third, the fairly well-developed coronoid processes are seen. 

 They consist of a series of three points in a row, on each side, one 

 behind the other, the anterior being the largest, the other two grad- 

 ually diminishing in size. 



The mesial aspect of either ramus is longitudinally concave for its 

 anterior third, while behind, it becomes flattened, to finally pass be- 

 neath the articular extremity, facing, as it does so, downwards and 

 towards the median plane. 



Viewed from above, we find the symphysis concave and more than 

 a sixth the length of the bone. In the median line behind, between 

 the ramal sides, it sends backwards a spike-like process, nearly 2 cm. 

 long, which we may call the posterior symphysial process, this is 

 present in A. candidissiina, but absent in some specimens o{ Nycticorax. 

 We also see it in very old Albatrosses. 



The articular ends above, are generally concave, but two small con- 

 vexities occur on the oblique line that crosses in front of the central 

 pit. A circular pneumatic foramen is seen at about where it occurs 

 in the majority of birds where it is present. The hinder ends of these 

 articular extremities are obliquely truncate, (Fig. 5), the faces looking 



