Rhynchocephalia. 29 
% • 
small ebony plates. The paddles, wliicli were four in number, each 
with five digits, had a remarkable resemblance to the “flippers” 
pf a whale ( see Fig. 33). 
Fig. 36. — The imperfect skull of Mosasaurus Ccmperi (Meyer), from the 
Upper Cretaceous ot Maestricht, Holland (much reduced). 
Order V.— RHYNCHOCEPHALIA (Beak-headed Lizards). 
This order has only one living representative, the genus 
Sphenodon ( Uatteria ), from New Zealand. Its earliest known 
ancestor, Palceohattevia , dates from the Permian. In external 
appearance the Rhynchocephalians were lizard-like animals. 
They have the quadrate bone of the skull immovably fixed by 
the proximal extremity to the pterygoid, the palate is closed 
anteriorly by the median union of the pterygoids; the pre- 
maxillse are never united. The teeth are acrodont, being anchy- 
losed to the jaws. Abdominal ribs are always present. 
Under the name of Rhynchosaurus articeps, Sir Richard 
Owen described and figured, in 1842, a very interesting reptile 
from the fine-grained white Triassic sandstone of the Grinsill 
quarries near Shrewsbury (Trans. Cambridge Phil. Soc., vol. 
vii., part iii., p. 355, pi. 5 and 6). 
The vertebrse are biconcave, but whilst in some characters ot 
the processes they resemble recent lizards, m others they present 
characters like those of the Dinosauria. 
The skull presents the form of a four-sided pyramid com- 
pressed laterally ; it is also remarkable for the beak-like 
prolongation of the premaxi llaries, which are pointed and re- 
curved, and must have been encased in a horny sheath, like the 
mandible of a bird of prey. , _ . . , 
It had also, like the still existing New Zealand lizard 
Sphenodon (. Hatteria ), to which it is closely allied, two rows of 
minute acrodont teeth, united to a sharp edge of the maxillary 
Wall-case, 
No. 8. 
Table-case,. 
No. 11. 
Wall-case. 
No. 7. 
Table-case, 
No. 12. 
Rbyncbo- 
saurus. 
Table-case, 
No. 12. 
