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The apophyses establish, by their number, five kinds of vertebrae. 
The first sort, the last of the neck and the first of the back, have a 
superior spinous apophysis, long and compressed ; an inferior, termi- 
nated by a concavity ; four articular, the posterior of which are short, 
and are directed outwards ; and two transverse, which are thick and 
short. Their bodies are longer than wide, and wider than high ; their 
faces are transversely oval. Those of the middle of the back have not 
the inferior apophysis, but resemble the preceding in everything else. 
The last of the back, those of the loins, and of the beginning of the tail, 
have no articular apophyses, and their places may be known by their 
transverse apophyses, which become elongated and flattened. The arti- 
cular surfaces of the posterior of these vertebra are nearly triangular. 
The next of the tail, besides their superior spinous apophyses, and the 
two transverse, have at their inferior side two small surfaces to receive 
the angular bone*, Cl’ os en chevron ). The articular surfaces of these 
vertebra are pentagonal. The next set, Plate XVIII. Fig. 8, differ 
from the preceding in not having any transverse apophyses. These 
form a large part of the tail. The angular bone, a, is not here articu- 
lated, but united into one body with the vertebra. The succeeding 
vertebra become more and more compressed at the sides ; and, as 
they approach the end of the tail, cease to have any apophyses at all. 
This series of vertebra gives opportunity to M. Cuvier to offer some 
important observations. The angular bone first claims his attention. 
Its great length, with that of the spinous apophysis, which is opposite 
to it, sufficiently prove that the tail of this animal was considerably 
extended vertically. The absence of the transverse apophyses from 
a considerable part of the length of the tail, prove, at the same time, 
that it was much flattened at the sides. Hence he concludes, that 
this animal was aquatic, and swam in the manner of the crocodile, 
* That which I have termed angular bone, and which is by the French designated by the 
term l os en chevron , is a bone, of which several are sometimes placed at the junctures of the 
vertebrae of the tail on their lower part, where they are disposed so as to form an angle, as in 
the letter V. 
