16 Osteological Studies of the Sub-Family Ardeince. 
pointing downwards, while below it the squamosal process juts 
out, and between the two, the crotaphyte fossa passes to the lateral 
aspect of the skull. 
In Nycticorax the supraoccipital region is carried to a point 
above, and is usually divided by a pronounced crest with rounded 
summit. A far broader strip separates the crotaphyte fossae from 
each other in the median line. 
The occipital condyle, although of the same shape, is rela¬ 
tively much smaller, and finally the posterior orbital peripheries 
can be seen peeping above the parietal domes, all these differences 
enumerated giving to these two skulls, even when only casually 
compared from this view, a very dissimilar look. 
In a number of minor details, principally referable to relative 
position and form, the points for examination within the brain- 
case present certain differences between the Night Herons and the 
genus Ardea. 
The mandible of the Herons offers us a number of points of 
interest for our investigation. 
In the Great Blue Heron (a bird that I have alluded to sev¬ 
eral times above as simply the Blue Heron ) the outer border of 
either ramas of the mandible for nearly two-thirds of the distance 
back from the apex is very sharp, and the middle third of the en¬ 
tire length of the bone, the ramal border is swelled just within 
this cutting edge, which enlargement has its mesial boundary de¬ 
veloped 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 an¬ 
teriorly, to be 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 ramas we see numerous minute fo¬ 
ramina 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 flat, 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 
