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 Dinoikerium 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, 2-2 in. Length of second premolar, 

 2-9 in. Width of second premolar behind, 2-6 in. Length of third or first true molar, 

 4- in. Width behind, 2 - 8 in. Length of fourth tooth (second true molar), 3 - 9 in. 

 Width, 3o in. Depth of jaw to alveolar margin at the second premolar, 9 - 2 in. 

 Depth at third tooth or first true molar, S - 7 in. Width of jaw at second pre- 

 molar, 5-1 in. Width at middle of fourth tooth, 6'4 in. Distance between the 

 upper margin of nientary foramen and alveolus of first premolar, 3'6 in. Distance 

 from inferior margin to first premolar, 4*75 in. 



Plate 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. — 31. Sivalensis. 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. — 31. 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. — 31. Sivalensis. Fragment of upper jaw, with 

 second ? true molar, presenting five ridges, with alternately disposed 

 crown mammillae. — 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, 65 in. Width, 2-9 in. 



Figs. 6 and 6 a. — 3Iastodon 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 31. Arvernensis and 31. longirostris, but 

 it most resembles the former in so far as the alternate disposition of the 

 crown mammilla? 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 in 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 

 ridge3 are connected by one or two stout conical mammillae, interrupt- 

 ing their transverse continuity, and alternating with the divisions of 

 the main ridges. The vertical furrowing of the enamel at b and c, 



D 2 



