286 PROBOSCIDIA. 
The fst molar tooth has a square-shaped crown, broad- 
est behind, divided into four mastoid tubercles, and aver- 
ages an inch in length, (antero-posterior diameter,) and 
three-fourths of an inch in breadth. The second has an 
oblong crown, supporting three pairs of mastoid tubercles, 
and averages two inches in length, and one inch one-third 
in breadth. The third tooth, which takes the place of the 
above when shed, has a square crown, with two pairs of 
mastoid tubercles, and an anterior and posterior basal 
ridge ; it averages a length of two inches, with nearly the 
same breadth, ranging from one inch and a half, to two 
inches and a quarter. The fourth tooth has an oblong 
crown, and supports three pairs of mastoid tubercles, with 
usually a large posterior tuberculate talon; its average 
length is two inches three-fourths; its breadth one inch 
two-thirds. The fifth tooth resembles the preceding, but 
averages four inches one-third in length, and two inches 
three-fourths in breadth. The sizth tooth supports four 
pairs of mastoid tubercles, and a posterior talon, usually of 
small size; its average length is six inches; its breadth 
three inches and a quarter. The seventh, and last molar 
tooth, has generally five pairs of mastoid tubercles, and a 
posterior tubercular talon; its average length is seven 
inches and a quarter, its breadth three inches and a third. 
The observed extremes of size of this complex tooth, which 
is subject to more varieties than the preceding teeth, is 
five inches and a half, and nine inches; in general the pairs 
of tubercles gradually and slightly decrease in size from 
the first to the last: in the small-sized specimens of the 
seventh molar the decrease is more rapid, and the fifth pair 
is reduced almost to a tubercular talon, which is succeeded 
by a small basal ridge ;* in the middle-sized teeth the fifth 
* The tooth in the lower jaw of the Mastodon angustidens, figured by Cuvier 
