1i4 GEOLOGICAL DISTRIBUTION 
much alike. The molars approximate to the type of those of 
Triconodon, but the anterior and posterior cones are relatively 
smaller. Like that of the last-named genus, the mandible of 
Fria. 29.—Inner view of the right ramus of the mandible of Phascolotherium buchklandi ; 
from the Stonesfield Slate. The outline shows the natural size. i, Incisors (one missing) ; ¢, 
canine; p, premolars; m, molars. The mylohyoid groove is seen near the lower border. (After 
Owen.) 
Phascolotherium is remarkable for the extremely low position of 
its articular condyle. In Amphilestes (Fig. 30) of the Stonesfield 
Slate the molars appear to be of the same general type as those 
of Phascolotherium, but are more numerous, although their exact 
number cannot be determined. A somewhat different type 
of lower molar is displayed by the genus Aimblotherium, of the 
Dorsetshire Purbeck, to which dmphitherium of the Stonesfield Slate 
was probably allied. This type of tooth is shown in Fig. 4 (8, 9, 
12) p. 31, and, as there stated, represents that modification of the 
tritubercular type known as the tubercular sectorial. The three 
primitive tritubercular cusps form what is known as the blade of 
the tooth, behind which 
there is the talon or 
Pp hypocone. A similar 
\o\1234 5 Bi 2 
1\ wets form of molar oceurs 
3 
Na 
eh in the existing Opos- 
sums and Bandicoots. 
Fia. 30.—Reversed inner view of the left ramus of the 
mandible of Amphilestes broderipi; from the Stonesfield 
Slate. Twice natural size. The restoration of the anterior 
teeth is conjectural, and the condyle is placed too high. 
The number of lower 
teeth in .fmblotherium 
ist 4, ec 1, p 4, m 
7-8. Numerous allied 
types, such as fchyro- 
don and Dryolestes occur in the Upper Jurassic of Europe or the 
United States, while from only one side of the jaw being exposed 
in each ease so-called genera like Séylodon and Stylacodon have been 
formed upon specimens showing the opposite side to that which 
is exposed in the types of Amblotherium and Amphitherium. The 
(After Owen.) 
