534 
ORIGINAL ARTICLES. 
5. M2. With the exception of the increased depth of the median 
groove and the larger size, I am unable to detect special character¬ 
istics in M 2. 
Measurements: 
Maximum . 
0) 
1-75 
(2) 
1T5 . 
(3) 
1T7 
(D 
53 . 
Ilford. 
Average 
1*57 
1*20 . 
1T2 
5-01 
Minimum . 
1-4 
IT 
9-5 
4*7 . 
Wookey Hole. 
6. M 3. The median groove in the last molar reaches its maximum 
depth ; the posterior area is either rounded off to join the posterior 
wall of the posterior collis, or, more usually, is slightly flattened, 
especially in the unworn tooth. The posterior collis is wider at the 
base than in the other molars, and of greater posterior extension. It 
is equal, or sub-equal to the median. 
Measurements: 
Maximum . 
(i) 
(2) 
(3) 
(4) 
2T 
1-2 
. IT 
5T5 . 
Wirks worth. 
Average 
1-69 
1T6 
. 1-09 
5-27 
Minimum . 
ITS 
1*2 
. 1*0 
4*85 . 
Wookey Hole. 
§ 7. The Upper Milk Molars. —The Upper Milk Molars # of 
JR. tichorhinus, four in number, and, with the exception of Dm 1, in 
plan resembling the true molars [§ 5. § 6-4, 5, 6.] differ from them 
in their far smaller size, in their valleys being relatively much larger, 
their colies much smaller, and in the second costa always being the 
higher. The median groove traverses the base of all. 
1. Dm 1 . The first Milk Molar t [fig. 1], of which I have seen 
only one example, presents four well marked costse (K) on its external 
surface, the first divided from the second by a broad Y-shaped 
depression, that from the third by the broad median groove (I), while 
a narrower and more shallow groove divides the third from the 
fourth. 
The anterior valley (A) is divided into three portions by the 
fused combing plates [Gr, H]. The first of these is a deep open 
cavity, the second the space intercepted by the combing plates, and 
lastly, at a higher level the inner and smaller cavity. 
The anterior collis (D) is split up as it were into two 
cusp-like portions of which the posterior is the higher, by the fused 
combing plates that enter into the internal surface of the tooth. 
The median collis (E) is very large, and the posterior valley (B) is 
far larger than the anterior (A). The anterior portion of the crown 
* The verticality of the colies, and the non-development of the anterior combing 
plate in fig. 125 of The British Fossil Mammals, prove that the tooth figured is not 
that of It. Tichorhinus. It probably belongs to R. hemitoeclius (Falc.) 
f Dr. Schmerling, Eecherches sur les Ossemens Fossiles decouvertes dans les 
caverne de la Province de Liege, Yol. ii. pi. xxiii. fig. 3, gives a figure. 
