DESCRIPTION OF PLATES. 51 



diameter of left tusk, 2-9 in. Vertical diameter of left tusk (approximate), 4- in. 

 Width across the condyles, 7 "6 in. Antero-post. diameter of condyle, & - 5 in. ; 

 transverse diameter of condyle, 2 - 5 in. Vertical height of condyle, 2 - 6 in. Antero- 

 post. diameter of occipital foramen, 2 - 8 in. ; transverse diameter of occipital foramen, 

 2 - 9 in. From anterior border of occipital foramen to niche of palate, 10'9 in. 

 From niche of palate to beginning of diasteme, 12 - 7 in. Height of the pterygoids 

 above the body of the sphenoid, 5"5 or 6" in. Width of outer surface of pterygoids, 

 7'7in. Length of two broken molars (surface), 11*7 in. Length of anterior or 

 penultimate, 4-4 in. ; width, 3-1 in. Length of back molar, 7'4 in. ; width, 3-2 in. 

 Width of palate between anterior molars, T6in. Width of palate, behind, 3 - 5in. 



Plate XXXIX. 



Fiff. 1. — Mastodon Perimensis. Lateral view of same skull as figured 

 in Plate XXXVIIL, described above.— B.M. 



Fig. 2. — Mastodon Perimensis. Palate view of same skull. — B.M. 



Fig. 3. — Mastodon Perimensis. Occipital view of same skull. — B.M. 



Figs. 4, 5, and 6. — Mastodon Sivcdensis. Fragment of small black 

 head, three different views. The specimen is very perfect in form, 

 without crushing, so far as it goes. The plane of the occiput meets 

 that of the frontal in a slightly rounded manner. The ligamentary 

 depression is placed about the middle of the occiput, and is not deeply 

 marked, consisting of a dividing crest, separating two diverging pits, 

 having a heart-shaped outline. The occiput is slightly convex across 

 and from base to top. The condyles do not project backwards as in 

 M. Perimensis. The posterior boundary of the temple (edge of 

 occiput) is inclined to be sharp. There is no tendency to occipital 

 -bosses as in Elephant. The occiput in some respects resembles that of 

 M. Ohioticus. There is a very obtuse convexity or boss on the middle 

 of the forehead between the temples. — B.M. 



Greatest width of occiput (the half doubled) 22" in. Height of occiput from 

 surface of condyles, 17' in. Contraction of brow between the temporals, 11 '8 in. 

 Interval across the condyles, 7'1 in. Antero-post. diameter of left condyle, 4 - l in. 

 Transverse diameter of left condyle, 2 -5 in. 



Fig. 7. — Mastodon Sivcdensis. Fragment of upper jaw with two 

 molars, broken end of incisives, and anterior portion of zygoma. From 

 a cast in B.M. 



Plate XL. 



Figs. 1 and 1 a. — Mastodon latidens. Second ? upper milk molar 

 with two ridges. — B.M. 



Length, 1-9 in. ; width, T4 in. 1 

 Figs. 2 and 2 a. — M . latidens. Third ? upper milk molar with 

 four ridges. — B.M. 



Length, 3* in. ; width, l - 8 in. 



1 In the Museum of the Royal College | in front. The second milk molar is 2 - in. 

 of Surgeons is the left side of the upper long by about 1*5 in. wide. It has three 

 jaw of a young Mastodon latidens con- main transverse ridges and a small 

 taining the first and second milk molars. | bourrelet ridge in front, and a heel 

 The anterior tooth is about l'in. long, | ridge behind. It expands very widely 



and '8 in. wide, and has two ridges with 

 a heel. The main ridge is transverse ; 

 the anterior one is an obtuse cusp. 

 The tooth is oval, the sharp end being 



in the direction of the orbit. A vertical 

 section shows something like the enamel 

 of another small tooth, \ inch long. — H.F. 



