250 SPARKS FROM A GEOLOGIST'S HAMMER. 



brown tufts, two to seven inches long, in connection with 

 the Shawangunk skeleton. The entire structure was truly 

 elephantine, and it lived as a contemporary of the mam- 

 moth. Peculiarities of the grinding teeth, however, led 

 Cuvier to establish a distinct genus for its reception. 

 The molar or grinding tooth of the elephant, in its usual 

 condition, consists of a group of hollow, flattened cylinders 

 of enamel-covered dentine, standing vertical to the grind- 

 ing surface, and arranged in a rather close series, extend- 

 ing from the front to the back of the molar, and all 

 cemented in one huge mass by a substance called cemen- 

 tum (see Figures, page 249). Each flattened cylinder, 

 while unworn on the crown, is closed up, but by wearing 

 it soon becomes open. The cylinders, moreover, ultimately 

 coalesce at the base of the crown, forming a common body 

 from which the roots proceed. Now, in the mastodon 

 (see cut) the vertical flattened cylinders begin to de- 



GRINDER OF MASTODON. PERSPECTIVE VIEW FROM THE SIDE. 



velop on the crown in a similar way; but they are fewer, 

 smaller and less compressed, and coalesce with each other 

 much nearer the surface of the crown. Hence no cemen- 

 tum is required to hold them together, and this substance 

 is scarcel}^ discoverable except upon the roots of the tooth. 



