137 



570. The lower half of the same molar tooth. At this part of the section the 

 lamellae are expanded in the middle, which gives them a rhomboidal 

 form in the transverse section. 



From the drift or pleistocene of Brentford. 



Presented by Sir Joseph Banks, Bart., P.R.S. 



571. A molar tooth of the right side of the lower jaw of the Mammoth, dis- 



playing the outer crust composed of the third constituent of the tooth or 

 the cement, which is partially decomposed and detached from the dental 

 plates. 



The abraded surface of the crown measures seven inches and a half in 

 length, and three inches and a half in greatest breadth, and shows the 

 margins of nineteen of the vertical plates. 



From the pleistocene sand near Bridport, Dorsetshire. 



Presented by H. B. JVay, Esq. 



572. The corresponding molar of the left ramus of the lower jaw of the same 



Mammoth, in which the partially decomposed state of the tooth demon- 

 strates the constituent substances, and especially the cement, in the same 

 favourable manner. 



From the pleistocene sand near Bridport, Dorsetshire. 



Presented by H. B. JVay, Esq. 



573. Portions of two of the lamellar divisions of the crown of the molar 

 of a Mammoth, with the intervening layers of the enamel and cement. 

 The fractured surface of the dentine shows the course of the dentinal 

 tubes to the naked eye, and the centres from which they radiate to the 

 surface of each of the terminal mammillae are continued down to the base 

 of the plate. 



From the fresh-water pleistocene beds of Grays, Essex. 



Presented by Prof. Owen. 



574. A single plate of the molar of a Mammoth from which a great part of the 

 cement has been removed, showing the vertically grooved and ridged 

 surface of the enamel ; each ridge is impressed by a fine groove. 



Locality unrecorded. 



Presented by Sir Everard Home, Bart, F.R.S. 



T 



