AND CLASSIFICATION OF THE FOSSIL REPTILIA. 
253 
Caudal VertehrcB Platypodosanrus. (Plate 17.) 
The only known example of the tail of an Anomodont is the specimen described by 
Sir PiCHAED Owen'''- as a mass of matrix, including part of the sacrum and pelvis, 
with ten anterior caudal vertebrae, probably a species of Dicynodon. It is from Fort 
Beaufort, a locality which yielded the skulls of Dicynodon Bainii, D. 'pardiceps, and 
D. feliceps, and it may not improbably be referred to one of these species. Unfor¬ 
tunately, the vertebrae have been separated from the sacrum and pelvic bones. The 
original description of the vertebrae is brief, and the figure unsatisfactory. The 
following notes contribute to a knowledg’e of this region of the vertebral column. 
The specimen includes eleven vertebrae, and measures 31 centiras. in length. The 
vertebrae progressively become smaller and shorter. All the earlier caudals have 
strong transverse processes, which are directed outward and very slightly downward, 
but the processes, which are separate ossifications, disappear from the later vertebrae. 
Where the transverse processes begin to decline, strong short chevron bones begin to 
be developed. These bones are massive, as tliough they supported the weight of the 
tail, and are in close contact with each other, but rapidly diminish in size, as though 
the tail only included about five more vertebrae ; though the total number may have 
amounted to twenty. 
In the first four vertebrae, each centrum is 3 centiras. long. In the next three, 
each centrum is 2‘6 centims. long, the eighth and ninth are each 2 centims., the 
tenth 1'9 centira., and the eleventli about 1'7 centim. long. 
With this shortening in length, the whole aspect of the vertebrae gradually changes. 
At first the centrum is evenly convex from side to side below the transverse processes, 
and somewhat markedly concave from front to back. The margins of the centrum are 
sharp. Its depth is 6'3 centims., and its transverse width about 5"7 centims., and 
the transverse measurement below the bases of the transverse processes is 4 centims. 
At the base of the fifth centrum, on the posterior border are two strong tubercles 
with a transverse measurement of nearly 3 centims., and a strong groove between 
them. On the sixth .centrum the tubercle on the right side is elongated into a 
process directed downward and inward ; on the left side the process is lost, being 
separated by suture from a lai’ge rounded boss. This is the beginning of the chevron 
bones. The chevron bones in the seventh and succeeding vertebrse are similar to 
each other. Each is a V-shaped bone which appears to articulate by two facets on 
the posterior face of the centrum. The transverse width over these processes is 
at first about 3‘8 centims., and in the last vertebra preserved it is reduced to about 
2‘6 centims. In lateral view the processes are directed downward and backward ; 
below the attaclunent their sides converge downward with a slight lateral concavity, 
and the anterior and posterior borders are strongly concave, so that the extremities 
of the bones are expanded from front to back. The length of the chevron bones is 
* ‘ Cat. Foss. Kept, of Soiitli Africa,’ 1876, p. 73. 
