Page 337. 
336 ON THE ANATOMY OF PLOTUS ANHINGA, 
raphe, which becomes ossified to form the above-mentioned bony style 
in the adult bird. (See Plate [20] XXVIII. fig. 1 a.) 
Before commencing the description of the cervical articulations of 
the Darters, it may be mentioned that the same condition is observed, 
only in a Jess marked degree, in the Cormorants, and still less in the 
Gannets and Pelicans. 
The first eight cervical vertebre (including the atlas and axis), 
when articulated together in such a way that all the articular surfaces 
are in their proper relations one to the other, form a continuous curve 
with a strong concavity forwards. So considerable is this curve, that 
when the beak of the bird is horizontal the axis of the peculiarly long 
eighth vertebra is parallel to that of the skull, or very nearly so. 
The curve is not a part of a circle, but is one which gradually aug- 
ments in acuteness from above downwards, its most considerable 
development being between the 7th and 8th vertebra, which are con- 
sequently articulated at a considerable angle with one another, more 
strongly marked than that between the 6th and 7th, and this, again, 
more decided than that between the 5th and 6th, and so on. 
The 8th and 9th vertebra articulate so as to form an angle exactly 
the opposite in direction—namely, with its genu directed forwards 
instead of backwards. The same is the case with the 9th and 10th, 
the 10th and 11th, the 11th and 12th, the 12th and 13th; more 
slightly so between the 13th and 14th, and the 14th and 15th; whilst 
the 15th and following until the last (the 20th), which with the one 
above it carries imperfect ribs, form almost a straight line with one 
another, being slightly bowed, with the convexity directed back- 
wards. 
With the exception of the atlas and the 6th and 7th, the cervical 
vertebre are peculiarly elongate, the 8th being more so than the others, 
as may be seen in Plate [18] X XVI. fig. 1. 
Donitz figures a pair of accessory bony bridges on the dorsal surface 
of the vertebra following the most lengthy one, which must evidently 
therefore be the 9th. He however, speaks of it as the 8th, which 
seems to me to be an error depending on the omission of the considera- 
tion of the atlas, because in Plotus anhinga (both from Brandt’s figure 
and my specimens) it is most certainly the 9th, as it is in Plotus nove- 
hollandie, Phalacrocorax carbo, and P. lugubris. I have, however, not 
seen Plotus levaillantii. 
Donitz attributes the peculiar kink of the neck of the Darters, 
which it is impossible to obliterate without lacerating the surrounding 
muscles, to the presence of the bony bridges he describes; in this, 
however, he is mistaken, it depending on the above-mentioned pecu- 
liarity in the 8th cervical vertebra, by which it is angularly articulated 
with the 7th and 9th vertebra, the upper genu being posterior, and the 
