Osteological Studies of the Sub-Family Ardein.ee. 
and bulky bone ; it spreads out a wide 
base for the frontals to rest upon ; its 
straight anterior upper margin bounds 
the cranio-facial hinge posteriorly ; its 
anterior surface is broad, bearing a del¬ 
icate medial crest, continued upon it 
from the apex of the rostrum. Its 
internal structure is cancellous, and 
air is undoubtedly admitted to per¬ 
meate it throughout. At a point, on 
either side, half way between the ros¬ 
trum and the roof, it supports a fee¬ 
bly developed wing, the lower spur 
of which meets the backward extend¬ 
ing process of the lower and smaller 
portion of thelacrymal. Among such 
birds as the Gannets and Pelicans the 
ethmoid becomes lamelliform again, 
and it is not nearly as thick, through 
and through in the Night Herons as 
we find it in Ardea. 
The middle third of the rostrum 
of the Blue Heron is a smooth cylin¬ 
drical rod, which posteriorly is grad¬ 
ually projected from the sphenoid to 
merge anteriorly into the ethmoid. 
The inter-orbital septum is very in¬ 
complete, presenting one large vacui¬ 
ty, with which the foramina for the op¬ 
tic nerves have united, together with 
the smaller nervous foramina found in 
many birds to the outer side of the 
latter. Above this interorbital vacuity 
we note that the olfactory foramen is 
also very large, and the grooves leading 
forwards from its anterior apex for 
the nerve is faintly double. In my 
specimen of Ardea candidissnna all 
these openings have merged into one 
* 1 , A 
ffc 
fit 
Fig. 4. 
Fig. 4. Superior view of the mandible, same specimen as shown in Fig. 3, where the 
hone is seen on left lateral aspect. Somewhat reduced. 
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