20 Osteological Studies of the Sub-Family Ardeince. 
The neural crests or spines of the seventeenth and eighteenth 
are thick and long, and interlock with each other by an extensive 
joint. 
In the eighteenth vertebra we observe for the first time a free 
pair of pleurapophyes, with very short bodies, but .still articula¬ 
ting by tubercula and capitula. 
Prof. Owen in speaking of the movement of these vertebrae of 
the cervical region upon one another, says: “ This mechanism 
is most readily seen in the long-necked waders which live on fish 
and seize their prey by darting the bill with sudden velocity into 
the water. In the common Heron, for example, ( Ardea cinerea ), 
the head can be bent forward on the atlas or first vertebra, the 
first upon the second in the same direction, and so on to the sixth, 
between which and the fifth the forward inflection is the 
greatest ; while in the opposite direction these vertebrae can only 
be brought into a straight line, From the sixth cervical vertebra 
to the thirteenth the neck can only be bent backward ; while in 
the opposite direction it is also arrested at a straight line ; from 
the fourteenth to the eighteenth the articular surface again allow 
of the forward inflection, but also limit the opposite motion to the 
straight line.” (‘Anat. of Verts., Vol. II, p. 39.’) 
This is precisely what I find in examining the same vertebrae 
in the neck of Ardea herodias. It can best be studied in the neck 
of a fresh specimen from which the skin has been removed, with 
the skeleton of the neck of another individual at hand for com¬ 
parison. 
The skeleton of the neck in Nycticorax differs in many par¬ 
ticulars from that of Ardea; a number of these points only be¬ 
come evident after careful comparison, and will not be taken up 
in detail here. Others show a profound difference in organization, 
such as—the first pair of free pleurapophyses occurring on the 
seventeenth vertebra instead of outlie eighteenth as in Ardea; 
the third, fourth, fifth and sixth vertebrae are not elongated as in 
Ardea , but show the simple gradation in size down the cervical 
chain ; finally, the inferior wall of the carotid canal is open in 
the last four vertebrae through which it passes, in Nycticorax , and 
only in the last in Ardea herodias. 
Returning to the nineteenth vertebra in the Great Blue 
Heron, we find that it has a high quadrate neural crest or spine 
which interlocks by a free joint with the one behind ; it sends 
