THE TORTOISE. 103 



this heavy coating is spread evenly over the surface of 

 the bones ; but in the Hawksbill Turtle,, it is modified 

 into a series of separate plates, which overlap each 

 other like the tiles of a house, or the surface of an 

 imbricated bud. They are rather leaf-shaped, the 

 pointed end projecting, and the blunter end fixed to 

 the skeleton. Altogether there are thirteen of these 

 plates in every Hawksbill Turtle, the complete set 

 being technically called a "head." One of these 

 plates, which is in my collection, is exactly a foct 

 long, by six inches and a half at its widest part. On 

 it are six circular scars, showing the places where 

 sessile barnacles have at one time established them- 

 selves. 



On turning it over, and looking at the edges, it is 

 easy to see how the plates are increased by successive 

 depositing of new substance around the edges, the 

 series of deposits being as clearly marked as the rings 

 in the wood of an exogenous tree. 



The whole of the upper surface is covered with 

 multitudinous scratches in all directions, showing the 

 rough usage which it must have endured during the 

 life of the animal, and when merely viewed from the 

 side it looks a very uninteresting object. A piece of 

 black horn or pasteboard would be about as handsome. 

 But, when it is held up to a good light, it is instan- 

 taneously metamorphosed, and becomes endowed with 

 the richest mottlings of red, brown, black, and 

 yellow. 



It is rather a remarkable fact that the horny cover- 

 ing is removable from the skeleton by means of heat. 

 The turtle hunters, therefore, who have not the least 



