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.' 1 



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 \ nat. size. 



of a straight, subcompressed 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 



retains its thin coating of cement : the decussating curvi- 



u2 



