KIMMERIDGE CLAY. 3 
Paleontologist’s mode of work is like that of Antiquaries of another order, who read 
inscriptions on Roman buildings by the nail-marks when the letters themselves have been 
wrenched off for the sake of the metal. 
Species—PLiOsauRUS GRANDIS, Owen. Plates I and II. 
PLESIOSAURUS GRANDIS, Ow. Report on British Fossil Reptiles, 8vo, p. 83, 1839. 
PLEIOSAURUS BRACHYDEIRUS, Ow. Odontography, 4to, p. 283 (?), 1840. 
The most complete example of the skull of a Pliosaur which has come under my 
observation was disinterred from the Kimmeridge Clay, at Kimmeridge, Dorsetshire, 
under the superintendence of J. C. Mansel, Esq., F.G.S., of Longthorne, in that county. 
This skull is also the largest of such specimens hitherto found’; and, since the matrix has 
been removed, it has yielded the most instructive characters of cranial structure and 
dentition. Originally sent to me by Mr. Mansel for determination and description, the 
specimen has since been presented by its discoverer to the British Museum. The same 
liberal donor has subsequently enriched the National Collection by a lower jaw and 
part of the cranium, with evidence of the locomotive organs of the Plosaurus trochan- 
terius. 1 shall premise to the descriptions some of the dimensions of both specimens. 
TABLE OF ADMEASUREMENTS. 
Pliosaurus grandis. Pliosaurus trochanterius. 
Feet. | Inches.| Lines. | Feet. | Inches. | Lines. 
Length of the mandible in a straight line from the fore 
end of the symphysis to the angle of the jaw 4) 8 — 4 4 _— 
Tb., following the curve on the outer side of the ramus 5 11 — 4 5 6 
Length of the alveolar series following the curve. ‘ 3 7 — 1 9 6 
Length of the “symphysis mandibule”’ 1 1 6 1 4 6 
Greatest breadth of ditto . : —_ 7 3 — 7 - 
Breadth at posterior part of ditto — 6 9 =e id, 4 
Depth of, at the same part — 5 6 —_— 3 9 
Depth of ramus anterior to articular surface : _— 4 3 — z | 9 
Breadth of mandible at the hind end of the alveolar | 
series . 1 11 — _ 8 8 
Length of cranium from the occipital condyle ¢ to the 
end of muzzle* . 4 9 — — a a 
Greatest breadth of premaxillaries, Viz., across the | 
fourth pair of alveoli. ' : -| — 6 9 ss = —- 
Breadth behind the fifth pair of alveoli. . Ae ay ee 6 = ia aa 
Breadth of cranium behind the alveolar series. : 2 l — ae == ad 
Length of palato-nares. : : : : < 5 = = = ae 
Breadth of ditto . =. 1 8 i a = 
Distance from their back part to end of occipital condyle —_ 6 5 — — — 
* The tympanic articulations for the lower jaw, which extend the cranium beyond the condyle, are 
broken off. 
