249, PROBOSCIDTA. 
Mammoth, from the unequal vertical extent of their plates 
above described, must necessarily exhibit the continuous 
undulating lateral lines of enamel when worn down. to 
a certain extent. 
1 Nat. size. Mammoth, Thames gravel. 
I have seen this structure in a few only amongst the nu- 
merous molars of the Mammoth examined by me, for teeth 
so worn down are rare. It is well shown in the remains of 
a very large molar, found in the beach near Happisburgh, 
Norfolk, which on a grinding surface of four inches nine 
lines in length, and four inches wide, shows seven dentinal 
plates worn down to their common uniting base of dentine, 
along the middle of the surface. 
It sometimes happens that the outer and inner margins 
of a plate, which are always deeper than the middle part, 
are not on the same transverse line, but one is inclined a 
little in advance of the other. In this case the abraded 
crown of the tooth, when worn down to the common 
middle base of dentine, displays an alternating disposition 
of the folds of the outer and inner sinuous lines of enamel. 
This variety affords grounds of the same kind and value 
for a distinct species of Mammoth as for the two other new 
species proposed by Mr. Parkinson. 
In old and much worn teeth the abrasion is sometimes so 
partial as to wear away the whole of the enamel on one 
