12 
Osteological Studies of the Sub-Family Ardeince. 
the group ; its anterior end is innermost, and it is intended to ar¬ 
ticulate with a corresponding surface on the mandible. 3. A 
smaller elliptical facet, with its axis parallel to the last, situated 
immediately across the valley referred to above. This is the low¬ 
est facet of the group, the skull being held with its superior sur¬ 
face, upwards. From the outer side of this facet a concave articu¬ 
lar surface is carried down, to extend partially across the anterior 
margin of the intervening valley. 4. A posterior elliptical and 
smaller facet, higher up on the bone than either 2 or 3 being di¬ 
rected somewhat backwards. A concave narrow articular isthmus 
connects this facet with No. 2, occupying the posterior margin of 
the intervening valley. 5. A large circular facet occupying the 
surface of the inner aspect of the foot of the quadrate, directed 
downwards, backwards and inwards, the shell being held as 
above. This facet is separated from 3 by a distinct valley. 6. 
On the inner angle of the foot of the quadrate, a small circular 
facet, directed forwards and upwards, intended for the cup on the 
posterior extremity of the pter} T goid. All these articular surfaces 
except the first and last, have corresponding elevations or depres¬ 
sions for their insertion on the articular end of the mandible, and 
I have risked the danger of being considered a ‘ ‘ dweller upon 
details” in order to show what an extensive array of facets the 
foot of this bone supports, and how complicated a surface it offers 
to the articular extremity of the mandible, I believe that a care¬ 
ful study of these facets, in the class birds, will some day afford 
us an additional series of facts that can be used with advantage in 
classification. 
The maxillo-palatines, the palatines, the pterygoids, and the 
condyle of the occiput, can all be seen on direct lateral view, but 
these I have reserved to describe in the two remaining aspects of 
the skull. 
Seen upon inferior view of the skull the superior mandible 
presents an unbroken horizontal surface. This is bounded on 
either side by its sharp edges, while its middle and longitudinal 
line is defined by a delicate and slightly elevated crest. At irreg¬ 
ular intervals on either side of the latter, minute foramina occur, 
from which spring branching concave venations, directed forwards 
and outwards to the lateral edges. Fig. 2. 
The dentary processes of this premaxillary bone are directed 
backwards, with pointed apices to overlap the major part of the 
