DESCRIPTION OF PLATES. 45 



Plate XXXIII. 



Fig. 1. — Mastodon Sivalensis. Lateral view of same skull as is 

 figured in Plate XXXII. Shows temporal fossa and left zygomatic 

 arch entire. — B.M. 



Fig. 2. — Palate view, showing palate, one molar on each side, both 

 zygomatic arches entire, occipital condyles, &c. Same cranium as fig. 1. 

 —B.M. 



Fig. 8. — Occipital view of same cranium, showing occipital condyles 

 and foramen, pterygoids, &c. — B.M. 



Fig. 4. — Lateral view of another cranium of M. Sivalensis, with 

 lower jaw in situ. The left zygomatic arch is broken away. — B.M. 



Plate XXXIV. 



Fig. 1. — Mastodon Sivalensis. Portion of skull showing palate with 

 two molars on either side, the posterior molar on right side imperfect. 

 In this specimen there are two large orbitary foramina and there is 

 only a tusk on the right side ; the left tusk-sheath is withered. The 

 tusk-sheaths are very divergent, with an enormous deep trough 

 between, and there is great concavity of the brow, as in E. insignia. 

 The teeth diverge anteriorly, as in Mastodon Ohioticus, but in a 

 less degree. The molars are excessively like Smith's specimen of the 

 last molar upper jaw, right side, of Mastodon Arvernensis (Plate 

 XXXVI. fig. 8). The slope of grinding surface from without inwards 

 is very notably seen (see Plate XXX. fig. 8). The anterior molar of 

 both sides is worn, but shows four ridges with a heel, the ridges so 

 advanced in wear as to exhibit the characteristic alternating discs of 

 wear, so remarkable in this species. The last molar is perfect, except 

 the heel ridge, on the left side. The front ridge is barely touched by 

 wear, while the four back ridges are intact. The drawing does not 

 show the characters very perfectly. The front ridge has two confluent 

 ridges on the inside and two on the outside, to the inner of which the 

 intermediate pillar is attached, joining on with the innermost large 

 point of the third ridge. This third ridge shows but one thick point 

 on the inner division and two on the outer, with the intermediate pillar 

 connecting the outer division of the third with the inner division of 

 the fourth ridge, and so with the last ridge. This diagonal connection 

 of the posterior surface of the outer division with the anterior surface 

 of the inner points of the next following ridge cause in wear the 

 alternate-like discs of detrition, which characterize the teeth of Mas- 

 todon Sivalensis. The same kind of arrangement holds in Smith's spe- 

 cimen of Mastodon Arvernensis. The points in M. Sivalensis are very 

 high and obtuse, and the apex of the ridges is high as compared with 

 the specimen in Mr. ~W. Ewer's collection. (See also antea, p. 117.) 



Length of two molars, right side, 9 - 2 in. Length of front molar, left side, 4 4 7 

 in. ; width, 2-8 in. Length of last left molar minus heel, 6 - 4 in. ; width, 3 - in. 

 Interval between teeth in front, 34 in. ; interval between teeth behind, 2 - 7 in. 

 Height of enamel crown, 2*3 in. Height of inner mammilla of second ridge, 1"8 

 in. Length of palate from niche to diasteme, 9"0 in. Antero-posterior diameter right 

 tusk, 3'0 in. ; transverse, 2 - 7 in. Width of base of muzzle at orbitary foramen, 

 14*0 in. Interval between the middle of the orbits, 19*2 in. Antero-posterior 

 diameter or height of left orbit, 4 - 8 in. 



Figs. 2 and 2 a. — M. Sivalensis. Fragment of upper jaw with molar 

 presenting six ridges, with same characters as in fig. 1. The two anterior 

 ridges only are touched by wear. The tooth is now cut into sections, 

 —B.M. 



