'194 Mr. Webster on the Strata lying over the Chalk. 



This ingenious and indefatigable collector has also lately ascertained 

 a number of fossil bodies found among them to be the excrescences 

 produced by insects on the branches of various trees ; and I have been 

 since favoured by him with a portion of the jaw of a crocodile found 

 in Sheppey ; a fossil extremely interesting, since it is the only instance 

 yet observed of the bones of this animal having been found in the 

 London clay. 



Almost the whole of the vegetable and animal remains are en- 

 tirely impregnated with sulphuret of iron, and the vestiges of shells 

 are chiefly casts in this substance. The quantity of fragments of 

 pyritous branches* and fruits is very great. 



Among the pyritous casts of shells I found one that much resembled 

 the lymneus, and another the planorbis, but too imperfect to decide 

 the species. It is proper however to mention, that in a late number 

 of the Journal de Physique, in a paper on freshwater shells by M. 

 Braarde, mention is made of three freshwater shells from Sheppey, 

 the lymneus, melania, and nerita. 



These shells however, which are very few in number, do not 

 prove the existence of a freshwater formation in this place similar to 

 those of the basins of Paris and of the Isle of Wight : being found 

 among the remains of vegetable and of marine animals, we may sup- 

 pose that they were carried down together with the branches of trees 

 and fruits by the numerous streams and rivers that must have flowed 

 into this gulph. 



Most of the best preserved organic remains are enclosed in the 



* It will be an interesting investigation for the experienced botanist to trace the living 

 analogues of these ancient productions of this part of the earth. Such of them as have 

 been recognized are found to belong to species now growing only in the torrid zone; 

 thus adding to the evidence afforded by the animal remains of the great change that must 

 have taken place in the climate. 



