DESCRIPTION OF PLATES. 47 
behind exactly opposite the point where the coronoid margin of the 
ramus begins to rise up, the fracture passing through the middle of the 
last molar, the anterior ridge of which is visible in situ in the jaw. 
A detailed description of the points of distinction between this fossil and 
the Dinotherium giganteum of Kaup is given in the memoir on Perim 
Island fossils —B.M. 
Length of fragment, 17: in. Length of four front teeth, 13°5 in. Length of first 
premolar, 3°5 in. Width of first premolar behind, 2°2in. Length of second premolar, 
2°9in. Width of second premolar behind, 2°6 in. Length of third orfirst true molar, 
4-in. Width behind, 2°8 in. Length of fourth tooth (second true molar), 3-9 in. 
Width, 3-5 in. Depth of jaw to alveolar margin at the second premolar, 9-2 in. 
Depth at third tooth or first true molar, 87 in. Width of jaw at second pre- 
molar, 51 in. Width at middle of fourth tooth, 6-4in. Distance between the 
upper margin of mentary foramen and alveolus of first premolar, 3°6 in. Distance 
from inferior margin to first premolar, 4°75 in. 
PLaTeE XXXVI. 
Figs. 1 and 1 a.—Mastodon Sivalensis. Fragment of upper jaw with 
(second) milk molar. 
Length of tooth, 2°6 in. 
Figs. 2 and 2 a.—M. Stvalensis. Fragment of upper jaw with two 
milk molars. (Second and third).—B.M. . 
Length of anterior tooth, 2°6 in. Width, 1:8 in. Length of posterior tooth, 4° in. 
Width, 2°3 in. 
Figs. 3 and 3 a.—M. Sivalensis. Portion of upper jaw, with frag- 
ment of molar. (First or second true m.).—B.M. 
; Length of fragment of crown, 4: in. Width,2-9 in. 
Figs. 4 and 4 a.—M. Sivalensis. Fragment of upper jaw, with 
second? true molar, presenting five ridges, with alternately disposed 
crown mammille.—B.M. 
Length of molar, 5°6 in. Width, 2-9 in. 
Figs. 5 and 5 a.—M. Sivalensis. Fragment of upper jaw, with 
penultimate true molar. Five ridges and a hind talon._-B.M, 
Length of molar, 6°5 in. Width, 2:9 in. 
Figs. 6 and 6 a.—WMastodon Sivalensis. Last molar, upper jaw, 
left side in plan and profile. It has six ridges and a hind talon, and in 
this respect it differs from both M/. Arvernensis and M. longirostris, but 
it most resembles the former in so far as the alternate disposition of the 
crown mammillz is concerned. The complexity of pattern is even 
greater than in the English Crag Mastodon.—Cast in B.M. 
Length of tooth, 7°8 in. Width, 3°3 in. 
Figs. 7 and 7 a.—Mastodon Arvernensis, or the English Crag Mas- 
todon. Left upper jaw of a calf, with the last milk molar beautifully 
preserved 7m situ, and the remains of the empty alveolus of the pe- 
nultimate milk molar in front of it. The crown is composed of four 
ridges with a front and hind talon, and a well-pronounced basal 
‘bourrelet.’ The three anterior divisions are more or less worn, 
especially along the inner side; the last ridge is nearly intact. The 
ridges are connected by one or two stout conical mammille, interrupt- 
ing their transverse continuity, and alternating with the divisions of 
the main ridges. The vertical furrowing of the enamel at 0 and c, 
D 2 
