530 
ORIGINAL ARTICLES. 
and coalescing with the fourth at the distance of 1*1 to 1*4 in. from 
the base. The 5th or posterior costa, separated from the fourth by 
an elongated Y-shaped groove disappears at a distance of from 0*9 
to 1*2 in. from the base of the crown. 
The anterior is much larger than the middle collis. Of the two 
valleys the anterior has its entrance from 0*7 to 1*1 from base, the 
posterior, widest posteriorly and roughly triangular in the unworn 
crowns from 0*6 to 0*8 inches. 
Measurements : 
(i) 
(2) 
(3) 
(4) 
Maximum 
1*5 
. 1*9 
. 1*8 . 
6*5 
W irksworth. 
Average , 
. 1*32 
. 1*8 
. 1*69 . 
5*66 
Minimum 
1*25 
. 1*6 
. 1*55 . 
5*2 
Wookey Hole. 
4. M 1. 
Of the 
4 costae on 
the exterior 
of Ml, in the unworn 
or slightly worn tooth the anterior is the most prominent, in those 
that are less worn, the anterior and the third. A groove deeper 
than the median divides the anterior from the second, while a broad 
shallow depression divides the 4th, or posterior costa, from the third. 
The upper portion of the latter is slightly flattened. The bases of 
the median and anterior colles are equal or sub equal in inward ex¬ 
tension, and consequently there is less difference between the antero- 
and postero- transverse measurements than in m 2. The entrance 
of the anterior valley is situated from 04 to 0*8 inches from the base 
of the crown. In one molar abnormal, in other respects it is 0*93. 
Measurements: 
(4) 
7.2 Wirksworth. 
6*49 
6*0 Wookey Hole. 
5. M 2. Of the 4 costae on the exterior of m 2 the third is the 
highest, the second, abruptly mapped off from the first by a deep 
furrow, dies down into the median groove, while the 4th is divided 
from the third by a broad shallow depression, dying away below. 
The anterior collis is by far larger than the median, and its base has 
a far greater inward extension than that of the latter. In both these 
respects it contrasts with m 1. The height of the entrance of the 
anterior valley from the base varies from 06 to 09, of the posterior 
from 07 to 1*1 inches. 
Measurements: 
Maximum 
a) 
175 
(2) 
. 2*5 . 
(3) 
2T . 
(4) 
7*7 
Wirksworth. 
Average . 
1-77 . 
. 236 * 
1-98 . 
7*07 
Minimum 
1-7 . 
2*0 . 
1*9 . 
6*7 
Wookey Hole. 
Maximum 
-p cement 
(i) 
1*6 
(2) 
. 2*33 
(3) 
. 2*0 
Average . 
1*54 
. 2*08 
. 1*9 
Minimum 
1*36 
. 1*95 
. 1*85 
