192 THE MICROSCOPE AND ITS LESSONS. 



masses of stone dung are found in beds about ten feet 

 below the earth's surface, which yield out of every 

 twenty pounds about three of coprolite that is, about 

 thirteen per cent. And here, in the same geological 

 division of our little world of wonders our cabinet of 750 

 microscopical objects, we have the fossil teeth of reptiles, 

 sharks especially, from the same beds, showing to what 

 families these pre- Adamite brutes belonged, in which the 

 ivory and dentine are in such excellent preservation that 

 a well-prepared specimen, cut exceedingly thin, will show 

 us more of the structure of the teeth than would one 

 taken from the mouth of a recently dead animal. Nay 

 more, in the fossil tooth of an ichthyosaurus of our 

 cabinet we have not only the original tooth, but, that 

 decaying, we may behold the new tooth arising in the 

 socket, ready to take its place when the decay is com- 

 plete ; * and all, in the course of ages, silently but so 

 perfectly absorbing the minerals, then in a state of semi- 

 solution, that ages after, when dug out of their graves, 

 the ivory cells are as clear to the eye, with the aid of the 

 microscope, as daylight. But we have not yet done with 

 our slice of coprolite. Yes, they are " bones," the broken 

 pieces of which you noticed in the half-digested mass of 

 partly excrementitious matter. You said rightly; but 

 observe, they are fish-bones, and they show that in 

 \\hatever body they were devoured as food, that body 

 must have been aquatic. But let us now employ our 

 higher power, and then we shall see the structure of 

 the fish-bone which formed part of the skeleton of the 

 smaller animal and which afterwards became food for the 

 larger ; and not the structure only, but the vessels which 

 supplied the structure itself with food, namely the blood. 



* This valuable specimen was obtained from a portion of jawbone of 

 ichthyosaurus from Lyme Begis, Dorsetshire. 



