176 



THE GEOLOGIST. 



alludes to the impossibility of the mastodon, with long upper 

 tusks, making use of inferior tusks such as those forming 

 the subject of the present discussion, and never exceeding 

 twelve inches in length ; but these tusks nevertheless bear, 

 Mr. Koch says, evident signs of having been employed in 

 rooting and grubbing ; and hence, he infers, that the animal 

 to which they belonged must have had equally short upper 

 tusks. For the purpose of illustrating his views, the author 

 proceeds to offer some remarks on three species of tetracau- 

 lodon, to which have been applied the names of T. Godmani^ 

 T. Kochii, and T. tapiroides. The first has been described 

 by Dr. Godman, its discoverer, and by Dr. Hays ; but Dr. 

 Koch calls attention to the characters presented by the max- 

 illary and nasal bones, as well as to the additional foramen 

 near the molar bone, and which is wanting in the mastodon 

 and elephant. Of the T, Kochii the author possesses an 

 entire upper jaw, with six molars and two tusks, found rest- 

 ing on the lower jaw, which contained a tusk undisturbed in 

 its alveolus. The upper tusks indicate, Mr. Koch says, 

 that they were designed to be used in harmony with the 

 lower tusk for rooting and grubbing. They are nineteen 

 inches long, more than one-third of the entire length being 

 concealed in the skull ; and their greatest circumference, 

 which is nine inches and a half, occurs at the apex, and not 

 on the base. The enamel on the root is very thin, but at 

 the opposite extremity it is uncommonly thick, and this part 

 bears indisputable proof of having been much used during 

 the life of the animal. Mr. Koch admits that the left tusk 

 disappears in the adult animal, but he says that both in the 

 old and young individual the tusks have the same pecuharity 

 of being equal in circumference at the root and farther extre- 

 mity, and that the " bulb for the reception of the nerve and 

 nourishment of the tusks resembles that of the upper tusks 

 minutely both in the old and young animals, which pecu- 



