46 FAUNA ANTIQUA SIVALENSIS. 
Figs. 3 and 3 a.— WM. Sivalensis. Fragment of lower jaw with portion 
of molar, four ridges and part of a fifth —B.M. 
Extreme length, 5-4 in. Breadth in front, 2°5 in. 
Figs. 4 and 4 a—WM. Sivalensis. Fragment of lower jaw, with 
three ridges of a molar.—B.M. 
Figs. 5 and 5 a.—M. Sivalensis. Fragment of molar.—B.M. 
PEATE XXOCVe 
Figs. 1 and 1 a—Mastodon Sivalensis. Fine specimen of lower 
jaw, with one molar on either side. A portion of the right ramus 
deficient, but restored in the drawing. The teeth show well the 
alternating discs of wear characteristic of the species, and two outer 
mentary foramina.— B.M. 
Fig. 2.— Mastodon longirostris (Kaup), from Eppelsheim; lower 
jaw in outline, profile view; from a cast. 
Figs. 8 and 8 a.—Mastodon Andium (Cuv.). Perfect lower jaw of 
an adult with two last molars in situ, from Buenos Ayres. The 
anterior tooth confirms what is shown by the Canterbury specimen 
(Plate XL. fig. 15) respecting the penultimate. It is in an advanced 
stage of wear, but exhibits distinctly the discs of three ridges. The 
crown is nearly rectangular in form; the dimensions being 5*1 in. in 
length, 2°35 in. of width in front, and 8: in. behind. The posterior 
tooth, which is the last or third true molar, has the crown composed of 
four principal ridges, and a complex sub-triangular heel of several 
points. The three anterior ridges are partly worn and exhibit well the 
characteristic complex trefoil discs of wear. The two posterior ridges 
are intact, and the sinuous hollows between them. show the very 
considerable layer of cement which is present in a greater quantity in 
this than in any other species of true Mastodon. The dimensions of 
this tooth are about 8 in. in length by 3°5 in. of width in front, 
whence it narrows gradually towards the posterior end.—B.M. 
Fig. 4.—Mastodon Ohioticus (Blumb.), from North America. Fine 
specimen of lower jaw with two last molars, viewed from above. The 
anterior or penultimate tooth consists of three ridges separated by trans- 
verse uninterrupted valleys; all the ridges are slightly affected by wear. 
The posterior tooth consists of four main ridges and a subordinate talon 
ridge; all untouched by wear.—B.M. 
Fig. 5.—M. Ohioticus. Profile view of same jaw. One large 
and one small mentary foramen.—B.M. 
Figs. 6 and 6 a.—Dinotherium Indicum (Fale.). Superb fragment 
of lower jaw, left side, with molars, brought from Perim Island by Miss 
Pepper. The specimen contains nearly the whole of the adult series of 
five molars in situ. The contour of the body of the jaw is shown in 
the most perfect state of preservation, the fossil having fortunately been 
mineralized by means of a very hard siliceo-ferruginous infiltration. 
But it has evidently been long rolled about on the sea-beach as a 
boulder, so that the crowns of the whole series of molars have been 
hammered off nearly level with the alveolar margin of the jaw; the 
curtace of the fossil is jet black, and almost all of the matrix has been 
cleared away, probably by the long-continued action of the sea, which 
has given it a semi-vitreous polish. Patches of recent marine shells 
are also found on the surface. The symphysis of the jaw is broken off 
about 24 in. in front of the anterior premolar, and the bone is truncated 
