MASTODON ANGUSTIDENS. 291 
are all from our crag-pits in the immediate vicinity of 
Norwich. I have also a large and curiously flattened 
portion of a tusk, which is about sixteen inches long; the 
structure is unquestionably ivory ; this our friend Professor 
Sedgwick said he should like you to see.” 
The specimen, of which figures are subjoined, is a portion 
Fig. 101. 
Portion of the lower tusk of the Mastodon angustidens, from the fluvio-marine 
crag, Norwich. a 4 nat. size. 
of a straight, subeompressed conical tusk: the base of the 
fragment is as solid as the apex, and the whole is traversed 
by a subcentral canal, of nearly the same diameter, which 
is about three lines, from one end of the fragment to the 
other. The outer layers of the ivory have been detached, 
excepting a very small portion near the small end, which 
curvi- 
retains its thin coating of cement: the decussating 
u 2 
