536 
ORIGINAL ARTICLES. 
the second is strongly marked, the third broad and ill-defined, and 
traversed in its upper half by a faint depression. The groove pos¬ 
terior to it is broad and shallow. The anterior valley (A) advances 
with scarcely any curvature straight to the anterior and outer angle 
of tooth. The combing (Gr H) plates are fused together except in 
one instance. The anterior collis (D) is much larger than the 
middle (E), and is deeply marked by the inner termination of the 
guard. 
Measurements: 
Maximum . T6 . 1*8 . 1'75 . 60 , Kents Hole. 
Average . . 1.51 . 1.62 . 1*57 . 5*8 
Minimum . . 1*4 .1*58.Wookey Hole. 
§ 8. Lower Milk Molars. —The two lower jaws from Thame 
and Lawford, in the Bucklandian Museum, already alluded to 
[§ 4,] and described by Professor Owen,* as containing the Pre¬ 
molar dentition, differ from the rami of the adult in the following 
points. The first tooth is situated far nearer the symphysis, all 
the teeth are much smaller in vertical height, the fangs are much 
less solid and more divaricant, with the exception of Dm 1, than in 
the permanent series. They in common with others that I have 
examined, by all these characteristics are shown to be young jaws 
containing the milk dentition, a portion of which (—Dm 3, and 4,) 
—I found in situ above Pm 3, 4, in the jaw of an adolescent animal 
from Wookey Hole. The argumentsf therefore based upon the 
hypothesis that these jaws contain the permanent dentition, and 
especially Pm 1, fall to the ground. The teeth in outline only, 
and general arrangement of valleys and colies [§ 6] resemble the 
permanent series. A glance, however, at the measurements of each, 
shows the vast difference between them. 
The fangs are 4, those of Dm 1 excepted, divaricant, excavated 
underneath, and connate as in the permanent lower molars. 
1. Dm 1. Pig. 5, 6, a and the median groove (I) faintly impressed 
on Dm 1 and extending from the apex of the crown to the 
posterior angle of the base cuts off an anterior area (M) twice 
as great as the posterior. The former of these is also divided 
by a faint diagonal depression into two costae, (K) of which 
the second is tumid, and more prominent than the first. Of the 
two valleys, the anterior (A) is but faintly impressed, the poste¬ 
rior (B) is deep, and constricted apically by the large posterior exten¬ 
sion of the median collis (E) as in Pm 2. The anterior portion of 
the crown presents a trenchant ascending slightly curved edge, the 
anterior collis (D) being very small and insignificant. The two con¬ 
nate fangs are either implanted in one alveolus, or in two with but 
a thin partition between them. Of unusual length and far more 
* Brit. Foss. Mam. pp. 337—342. Figs. 128, 137. 
f Op. cit. pp. 363, 364. 
