1020 MR. D. M. S. WATSON ON THE CHELONIA. 
Not only is this the ease, but in many respects it hasa resemblance 
in details even to modern Cheijonia which is very remarkable. 
For instance, the long and extremely slender vertebrx are quite 
tortoise-like, and in the fact that the capitular facet is placed very 
far forward on the centrum we have a suggestion of that inter- 
central rib-articulation which is so striking a feature of the 
mid-dorsal region of modern Chelonians. The way in which this 
rib-articulation travels backwards on the posterior dorsals is 
exactly similar to the condition in Homopus. The anterior 
position of the neural arch on each dorsal centrum is prophetic of 
the modern Chelonian arrangement in which each arch stands on 
two centra. The loss of a definite tuberculum on the dorsal ribs 
is suggestive of the complete loss of that articulation in Chelonia. 
The development of a short, powerful ulnar crest on the 
humerus and the slight upturning of its head are also re- 
semblances to the same group. 
In fact, although our knowledge of Hunotosaurus is too small to 
admit of a definite statement to that effect, it is by no means 
improbable that it is an actual ancestor of the Chelonia. Whether 
it be or not it does, I think, give us a great many suggestions of 
the changes which must have taken place during the development 
of the Chelonian shell and all that it implies. 
T have to thank Drs. A. Smith Woodward and C. W. Andrews 
for their kindness to me during my work at the Natural History 
Museum, and Dr. L. Péringuey for permission to examine the 
South African Museum specimen of Hunotosaurus. The Rev. J. 
H. Whaits was the finder of R. 4054, the best existing specimen 
of this rare type. 
Finally, my discussion of “ Archichelone ” owes much to the 
well-known work of many authors, amongst whom Drs. L. Dollo, 
O. P. Hay, W. R. Weiland, and J. Versluys are specially 
noticeable. When discussing so complex a subject as Chelonian 
ancestry it is impossible, if the result is to be at all clear, to 
attribute each part to its original author, a fact which must be 
my excuse for not acknowledging my indebtedness in detail. 
EXPLANATION OF PLATE VII. 
Eunotosaurus africanus Seeley. 
Fig. 1. Dorsal view of specimen No. 49423. .S., lateral scute; M.S., median 
scute. 
2. Ventral view of same. Cl., clavicle; Cov., coracoid; H., impression of 
humerus ; J.Cl., interclavicle; Sc., scapula. 
3. Lateral view of specimen No. R.4054. I7.,ilium: Sec., scapula; I-iX., ribs. 
4. Oblique dorsal view of same; I-X., ribs. 
All the figures rather less than natural size. 
