522 MONODON. 
This specimen was purchased at the sale of Mr. Park- 
inson’s collection by the Earl of Enniskillen, who most 
kindly transmitted it to me to have the figures taken 
from it which are placed at the head of the present sec- 
tion. ‘The specimen has lost much of the original animal 
matter, is absorbent, rather friable, and partially decom- 
posed, so that the layers of the basal substance of the 
dentine might be easily separated. In what length of time, 
simple exposure to the elements on the sea-shore would 
produce this state of decomposition, I know not; but 
I have only witnessed such a state in fossils of the age 
of the post-pliocene extinct Mammals. 
The fragment above figured is the basal part of the tusk ; 
it measures ten inches and a half in length, and nine inches 
in circumference: fig. 215, *, shows the short and wide 
conical pulp-cavity at the inserted end, and fig. 215, * 
the opposite fractured end, where the pulp-cavity begins 
? 
again to expand as it extends into the exserted part of 
the tusk. The superficial spiral ridges precisely resemble 
those at the same heavy implanted part of the tusk in 
the recent Narwhal. 
A portion of a fossilized tusk of a Narwhal is preserved 
in the museum of Comparative Anatomy in University 
College, and is said to have been obtained from the London 
clay in the neighbourhood of the metropolis.* A portion 
of the skull of a Monodon monoceros is said to have been 
found in the marine silt of the marshy plain called Lewes 
Levels. 
Cuvier mentions a fragment of the Narwhal’s tusk, 
considerably altered in texture, which is preserved in the 
museum of Natural History at Lyons, and cites a notice 
of similar fossils found in Siberia, 
* Professor Grant, in Thomson’s British Annual, 1839, p. 269. 
