46 FAUNA ANT1QUA SIVALENSIS. 



Figs. 3 and 3 a. — M. Sivalensis. Fragment of lower jaw with portion 

 of molar, four ridges and part of a fifth. — B.M. 



Extreme length, o~± in. Breadth in front, 2 - 5 in. 



Figs. 4 and 4 a. — M. 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. 



Plate XXXV. 



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. 3 and 3 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*85 in. of width in front, and 3 - in. behind. The posterior 

 tooth, which is the last or third true molar r 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 (Bhunb.), 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 (Falc). 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 wdiole series of molars have been 

 hammered off nearly level with the alveolar margin of the jaw ; the 

 surface 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 2-| in. in front of the anterior premolar, and the bone is truncated 



