ON THE MOLAR SERIES OE RHINOCEROS TICHORIIINUS. 535 
presents an ascending trenchant edge. The posterior surface is 
rounded and flattened. Of the four fangs the anterior and posterior 
pair are respectively fused together, as in the lower molars. 
Measurement: 
(1) (2) (3) (4) 
Wookey Hole 0 - 8 . 05 . 0'8 . 27 
2. Dm 2. [fig. 2] The second Milk Molar bears four and 
sometimes 5 costae (K). The groove between the first and second 
is by far the deeper. The anterior collis (D), small and slightly 
curved, is sometimes divided from the exterior lamina (L) by a 
depression. Anterior to the point of juncture is a broad trenchant 
plate in the unworn and partially worn tooth overlapping the pos¬ 
terior and outer edge of Dm 1. The median collis (E) is divided 
from the posterior (E) by a depression in the unworn tooth. The 
entrance of the anterior valley is wide, and partially blocked up by 
a cusp ; and in all that I have examined there are small vertical folds 
on the posterior wall. The combing plates are fused together insu¬ 
lating the accessory valley (C ), the walls of which are sometimes 
minutely folded. 
Measurements : # 
(i) (2) (3) (4) 
Wookey Hole 1*2 . 12 . 1*1 . 3 9 
„ . 12 . 12 . 115 . 4*0 
3. Dm 3. f (fig. 3) Of the four costae of the third Milk Molar 
the second (K 2), round and tapering, is mapped off from the first 
by a deep Y-shaped groove. It extends to the summit of the 
anterior as the faint and low third does to that of the posterior area. 
The median groove (I), inclined a little forwards, is well marked, and 
posterior to it is a faint elevation in the upper half of the tooth. 
The posterior wall of the anterior valley (A) is folded; its entrance 
is wide and sometimes blocked up by a cusp. The accessory valley 
(C) is completely insulated by the fused combing plates. The 
guard strong, but irregular at the inner side of the anterior aspect, 
and broken into cusps, is continued on the plate that overlaps the 
preceding tooth, as in Dm 2. 
Measurements: 
(1) (2) (3) (4) 
Maximum 1-4 . 15 . 1-4 . 5 0 Wookey Hole. 
Average 1-3 . 1*48 . 1'38 . 4*8 
Minimum 1*32 . 1-42 . T26 . 47 Wookey Hole. 
4. Dm 4 . (fig. 4) Of the four costae (K) of the last Milk Molar, J 
* I am unable to give average measurements, as, with the two above exceptions, 
all I have examined arc germs with the base of crown more or less broken, 
f Comp. fig. 7, pi. xxiii. of Dr. Schmerling. Op. cit. 
j Comp. pi. xxiii. fig. 10, of Dr. Schmerling. Op. cit. 
