IRON SAND FORMATION. 37 



In other parts of England, the Iron sand contains nautili, ammonites, 

 belemnites, ostreae, terebratulae, and numerous varieties of spongitae, and 

 other zoophytes*; but of these no traces exist in the sand of Sussex. 



VI. 



§ 1, 2. Limestone of Tilgate Forest. 



The strata that form the subject of the following observations possess 

 a high degree of interest, and constitute one of the most important series 

 of deposits in this part of the kingdom. Tlie nature and variety of their 

 organic remains, and the general resemblance which they bear to those of 

 the Purbeck limestone, and Stonesfield slate, have led me to an assiduous 

 investigation of their history. 



I have however to regret, that the distance of my abode from the tract 

 of country in which they are situated, has presented serious obstacles to 

 an accurate determination of their geographical dimensions ; but I have 

 spared neither pains nor expense to obtain a general knowledge of their 

 fossil remains, and geological relations. 



As these strata are of inconsiderable extent, and hold an intermediate 

 situation between the Iron sand and the Weald clay, appearing to repose 

 upon the former, it seems probable, that they are either a local deposition, 

 formed in an excavation, or basin, of that deposit ; or a protrusion of the 

 Purbeck beds, which he beneath it. Without however, deciding in fa- 

 vour of either supposition, it has been thought expedient to describe these 

 strata in a separate section; and for the present, to distinguish them by a 

 term derived from the central locaHty of the area they occupy on the 

 surface. 



The strata of Tilgate forest consist of various layers of sandstone, hme- 

 stone, and calcareous slate, lying on a bed of blue clay, of very consider- 



* Phillips' Outlines, page 140. 



