MA.STODON (ante). The mastodons are distinguished from the elephants princi pally by theirdentition. As in the elephants, the upper incisors grew from permanent pulps and constituted the tusks. In most cases, moreover, the mastodons have lower incisors, and these often formed short tusks, which, however, usually disappeared in the adult. But the more important distinction is found in the molar teeth, which are more numerous in the mastodon, and have nipple-shaped tubercles. These tubercles are in rows, the number of which varies in different species. For this reason Dr. Falconer divided the mastodons into two principal sections, trilophodon and tetralophodon. In trilophodon are mastodon giganteus, of the post-pliocene of North America; M. tapirokies and .11. angus tidens of the miocene, in which there are three rows of tubercles. In t3tralophodon are 111. latidens and M. longirostris of the miocene, and arvernensis of the pliocene, which the molars have four rows of tubercles. In M. siva,lensis from the upper miocene of India the molar teeth have five rows, and the last six rows of tubercles. For this Dr. Falconer proposed the name of pentalophodon. The distribution in time of the mastodon differs in the two hemispheres. In Asia and Europe the genus commenced in the miocene and became extinct in the pliocene. In America no fossils of them have been found previous to the pliocene. but they continued to the end of the post-pliocene period. The mastodon gigante-as of North America ranged from Canada to Texas. The most complete skeleton perhaps which has been found was discovered in 1845 at New burg, Orange co., N. Y., in a swamp usually covered with water, and described by Dr. J. C. Warren, of Boston, in which city the skeleton now stands. In this specimen the cranium is flatter than in the elephant, narrow between the temporal fossm, the face becom ing inuch wider below the nasal opening. The temporal fossm are very large, indicating great power in the muscles of the jaws. The cervical vertebrze have short spinous proc
esses, except the last, which is 6+ inches. The spinous process of the third dorsal vertebra is 23+ in. long. the others gradually becoming less, the last being 4 inches. The first lumbar vertebra measures, across the transverse processes, 17 in., the bo:ly measuring 5 inches. The sacrum consists of five bones and is 20 in. in length on the lower surface. The caudal bones probably numbered about 22, and were very strong at the commencement of the tail. There are 20 ribs, 13 true, and 7 false or floating. The first one is 28 in., and the ninth, the longest, 541- in. long; the last is 21 inches. The shoulder-blade is more nearly equilateral than in the elephant, and the glenoid cavity, for the reception of the head of the humerus, is 11 by 5 inches. The humerus is 39 in. in length and the same in its largest circumference. The circumference of the elbow joint is 44 inches. The radius is 29 in. long and 6+ in. wide at the lower end; the ulna. larger and 34 in. long. The fore foot is nearly 2 ft. broad. The thigh-bone, abolit the len,gth of the humerus, is 17 in. in circumference at the middle and 30 in. at the lower end; the knee-pan is nearly globular; tibia 28 in. long, 30 in. in circumference at the upper end where it articulates with the thigh-bone, and 131 in. at the middle. The skeleton is 11 ft. in height and 17 ft. long frorn end of face to commencement of tail, which is 6 ft. 8 in. loug. The circumference of the skeleton around the ribs is 16 ft. 5 in., and the tusks are 11 ft. long. 8 ft. 8 in. projecting beyond the sockets. About 30 species of inastodon are described by Dr. Warren in his work The Mastodon Giganteus of Yorth America, 2d ed. 4to, Boston, 1855. A species similar to the giganteus existed. during the same time in South America, dlso species belonging to the European type.