TAB. XVI. 
Plesiosaurus HawJdnsii, nat. size. 
Fig. 
1. Oblique side view of skull. 
2. Under view of skull. 
In comparison with the skull of Plesiosaurus doUcJiodeirus, Tabs. II and III, 
these figures exemplify the specific distinction of Pies. Mawkinsii in the greater 
longitudinal extent of the temporal fossae, and in the greater relative length and 
slenderness of the muzzle or facial part of the skull, the sides of wdiich converge 
at a more acute angle and are more concave. The symphysis of the mandible 
is longer in PI. Hawldnsii. The teeth in both jaws are relatively larger and longer 
in Plesiosaurus dolichodeirus. As compared with Plesiosaurus rostratus. Tabs. IX 
and XIII, the facial part of the skull is relatively shorter in Plesiosaurus Hawkinsii ; 
the pterygoids do not extend quite so far back; the “ palatonares,” Tab. XVI, 
fig. 2, r, r, are smaller, with more rounded ends of the ellipse. 
The following bones are indicated by the figures : 
1. Basi-occipital. 
2. Par-occipital. 
7. Parietal (near the “foramen parietale ”). 
7'. Ib., “ supra-mastoid process.” 
8. Mastoid. 
11. Frontal. 
15. Nasal (above the external nostril). 
20. Palatine. 
24. Pterj'goid. 
25. Ecto-pterj''goid. 
26. Malar. 
27. Squamosal. 
28. Tympanic. 
31. Angular. 
31'. Splenial. 
33. Dentary. 
The skulls here figured are from the Lias of Street, Somersetshire. In the 
British Museum. 
