TROGONTHERIUM CUVIERI. 185 
than the Huropean species, which itself surpasses in size the 
Beaver of North America. The length of the Siberian skull, 
from the occipital ridge to the most convex part of the inci- 
sors, was seven inches three lines. The chief difference 
which Cuvier recognized in the drawing was in the pro- 
portion of the last molar tooth of the upper Jaw, which 
was longer, instead of being, as in the Beaver, shorter than 
the rest. 
The first indication which presented itself to me of the 
Trogontherium as a British fossil, was from a fine speci- 
men of the incisor of the lower jaw in John Hunter's Col- 
lection of Organic remains in whose manuscript catalogue 
it is described as ‘a long cutter of the Scalpris-dentata, or 
Glires genus, from Walker’s Cliff, Norfolk.” This tooth 
measures five inches and a half in length, and must have 
exceeded six inches when perfect, but it has suffered mu- 
tilation at both ends. 
The chisel-crowned incisor in the lower jaw of the Tyo- 
gontherium (fig. 71) measures seven inches, following the 
outer curve from the root to the abraded summit. This 
magnificent relic of the gigantic Beaver, which is now in 
the British Museum, was discovered by the Rey. Mr. Green, 
of Bacton, in that interesting lacustrine formation, with 
the submerged forest, which is noticed at p. 25: it was 
taken out of the bed of reddish sand which, at Ostend, 
has been spread immediately over the chalk. The in- 
cisive tooth is longer and stronger in proportion than in the 
existing Beavers, and doubtless operated with proportional 
effect upon the members of that ancient forest when they 
were green and flourishing. The projection of the crown, 
or exposed part of the incisor, is such, that the distance 
between its summit and the anterior border of the first 
molar is as great as from this part to the articular con- 
