37 



still pour down its turbid waters in the same direction, and 

 carry seaward the same species of alligator, in which case 

 their bones might be includud in marine as well as in sub- 

 jacent fresh-water strata. The iguanodon was first dis- 

 covered by Dr. Mantell, who tells us it was an herbivorous 

 reptile, and regarded by Cuvier as more extraordinary than 

 any with which he was acquainted. The teeth, though 

 bearing a great analogy in their general form and crenated 

 edges to the modern iguanas which now frequent tho 

 tropical woods of America and the West Indies, exhibit 

 many striking and important differences ; for the teeth of 

 the fossil iguanodon have often been worn by the process of 

 mastication, whereas the existing herbivorous reptiles clip 

 and gnaw off, but do not chew, the vegetables on which 

 they feed. Fish have also been found in the wealden, but 

 the only species I have met with is the lepidotus, of which 

 two fragments are submitted for your inspection — one pro- 

 cured from Egerton by Mr. Chambers, of Pluckley, and the 

 other from Headoorn by me. ''"he lepidotus is allied to the 

 lepidostcus, or gir-pike, of the American rivers. The 

 whole body was covered with rhoraboidal scales, very thick, 

 and having the exposed parts coated with enamel. Most 

 of the species of the genus are supposed to have been either 

 river-fish or inhabitants of the sea at the mouths of estuaries. 

 The shells of a species of paludina, closely resembling the 

 P. vivipara of English rivers, abound in bands of limestone 

 called Bethersden marble, among which, plentifully scat- 

 tered through the woaldea clays, are shells of the cypris, a 

 genus oi crustaceans abounding in lakes and ponds ; and 

 we often find shells of cycUs, unio, and other fresh-water 

 and brackish-Water shells. This deposit, after being over- 

 laid by the grccnsaud and gault, was arched over 

 with chalk, extending from the north downs to the south 

 downs ; but the theory and the proofs of the denudation of 

 the weild, although interesting to geologists, are not likely 

 to prove interesting to a mixed assembly ; and we will, 

 therefore, step out of tho woalden lo the lower greensand, 

 or Kuutisb rag, which is a marine deposit and at the bottom 



