180 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



been recently obtained, as well as the result of Mr. Simms's measure- 

 ment ; and shall now mention some of these additions, beginning at 

 the junction of the Lower Green Sand with the Wealden, and 

 referring for an account of the junction itself to the abstract pub- 

 lished in the " Geological Proceedings," vol. iv. p. 198. The sub- 

 division of the strata into groups is, of course, in a great measure 

 arbitrary, and would, in all cases, probably vary, according to the 

 views of different observers, and to the temporary condition of the 

 cliffs, which are in a constant state of degradation and change. 



§. Although the two lower beds immediately over the Wealden are 

 not together more than 5 feet in thickness, it will be expedient 

 to consider them separately, both on account of the great number 

 of very remarkable fossils which they contain, and of their 

 difference, both in composition and fossils, from the beds of clay 

 immediately above, — which nearly resembles fullers' earth, and 

 differs much in its characters from the sandy clay or mud imme- 

 diately in contact with the Wealden. It is not improbable that 

 these two lower beds at Atherfield may be the representatives of 

 some more largely developed group at the bottom of the Green 

 Sand in other countries. 



The absence of strata corresponding to these lowest beds, in the 

 clay immediately above the Wealden at Hythe, is remarkable ; but 

 the bottom of the series in Kent is hitherto known only from 

 the specimens obtained from Mr. Simms's shaft. It is much to be 

 wished that this part of the section may be brought into view by 

 an open cutting, for which the vicinity of the town of Hythe 

 affords many promising positions. 



The list of fossils from the coast at Atherfield has received 

 several additions since my last communication ; among others many 

 excellent specimens of Perna Mulleti have been obtained, by which 

 some new points in the structure of that remarkable fossil are 

 supplied. The whole collection of fossils from this place has been 

 examined and named by Mr. Forbes. 



§. With respect to the clay to which the name of " fullers'-earth" 

 has here been assigned, I wish to correct a statement in my former 

 paper (Geol. Trans. 2d ser. vol. iv. p. 196.), where it is said that "the 

 " lowest stratum of clay immediately above the fossiliferous stone at 

 " Atherfield appears to be the equivalent of the fuller £ -earth of Sur- 

 " rey," and that the stone itself, about 2 feet in thickness, " is appa- 

 " rently the equivalent of the limestone very near the bottom of the 

 " Lower Green Sand at Hythe" This clay, though it has many of the 

 properties of fullers'-earth, is certainly not the representative of the 

 substance which bears that name at Nutfield and Reigate,in Surrey; 

 and the stone beneath is quite distinct from the Kentish Rag of the 

 Hythe quarries. I was led into both these errors by an imperfect 

 acquaintance with the bottom of the section at Hythe ; by the (sup- 

 posed) absence there of fullers' earth above the limestone ; and by 

 finding at Atherfield Nautilus radiatus (?), with Trigoniae and other 

 fossils of frequent occurrence in the Hythe stone quarries. The true 

 place of the fullers'-earth, at Nutfield itself, is above the Kentish 

 Rag, and considerably above the bottom of the Lower Green Sand. 



