SECTIONS OF TEETH. 213 



See f Transactions of the Microscopical Society/ vol. ii, 

 part ii, p. 46. 



The following preparations of bone may be obtained at 

 Baker's, and most other opticians : 



Femur of Poliocephalm 



Edwardsi. 

 Femur of Monkey. 

 Femur of Eagle. 

 Bone of Alligator. 

 Bone of Turtle. 



Rib of Python. 

 Eib of Tortoise. 

 Horn of Rhinoceros. 

 Seal bone. 

 Bone of Antelope. 



FIN-BONE OF LEPIDOSTEOS. 



A genus of fishes belonging to the family of Clupeidse, 

 natives of tropical America. They are remarkable for their 

 long rasp-like teeth and the hard scales like stone. They 

 are, with the genus Polypterus, the only living representa- 

 tives of the vast numbers of extinct voracious fishes whose 

 remains are found in various secondary formations. 



FEMUR OF TETRAO UROGALLUS. 



Tetrao urogallus, one of the Grouse tribe, an English 

 species of bird called Cock of the "Wood. 



SECTIONS OF TEETH. 



These are brilliant polariscope objects, and offer the 

 same interesting subjects for observation and comparison 

 in various animals, fish, reptiles, and mammalia. 



The teeth of Mammalia consist of a crown, or that por- 

 tion above the jaw-bone and gum ; and a neck, or narrower 

 intermediate portion. 



The substance of human teeth consists of three parts : 

 tlie ivory or dentine, which is white, and of a silky appear- 

 ance, composed of numerous tubes or canaliculi, called 

 ivory tubes ; the cement, or bony portion, which forms the 

 outer coating of the fangs, and is like other bone with 

 lacunae, but rarely with any Haversian canals ; the enamel, 



