244 RAMBLES OF A NATURALIST. 



seems to bear an inverse proportion to their size and 

 the degree of development manifested in their or- 

 ganisation. The higher animals, or, in other words, 

 those in which the animal machine had arrived at 

 its highest degree of perfection, have left but fee- 

 ble traces of their existence. We know of only 

 three or four cases in which osseous debris have been 

 found to contain the remains of the Monkey tribe, 

 while in the case of Mastodons*, Elephants, and even 

 gigantic Reptiles f, very few perfect skeletons have 

 been found ; and science has therefore gratefully 

 treasured the isolated fragments of their remains 

 which from time to time have been brought to light. 

 The inferior animals, on the contrary, have con- 

 tributed most materially in forming the solid crust 

 which we inhabit. In the case of certain mountains, 

 more than half their structure consists of shells, 

 whilst some entire strata are exclusively composed 

 of infusoria, which are so infinitely small that 

 hundreds of their carapaces crumble into dust 

 beneath the point of a needle. The study of these 

 inferior beings, which is so important to the phy- 



* [A note on the Fossil Remains of the Mastodon is transferred 

 to the Appendix, Note XIV.] 



f The Reptiles preceded the Mammals on the surface of the 

 globe, and they were present in a highly developed state during 

 the secondary period. Among the species then existing, several 

 possessed very strange forms ; amongst others we may instance the 

 Plesiosauri, which lived in the water, and had the body of a lizard, 

 with a serpent's head on a very long neck ; and the Pterodactyli, 

 which flew like bats, by means of a membrane, supported by one 

 of the digits of their anterior members, &c. Many of these species 

 were of very large size ; some of them being, according to Cuvier, 

 upwards of fifty feet in length. 



