310 GEOLOGY OK THE ISLE OF WIGHT. 



have retained after their original exposure to 

 attrition, in the river by which they were trans- 

 ported and imbedded in the strata. Thus those 

 parts which would afford the most valuable infor- 

 mation to the anatomist become entirely defaced, 

 and the specimens are for the most part water- 

 worn masses of bone, indicating only the enormous 

 magnitude of the animals to which they belonged. 

 The bones even when imbedded in the sandstone 

 and sand, are in general abraded, from having 

 been transported by water from a considerable 

 distance ; those in the clays are commonly less 

 injured, from the plastic material with which they 

 were enveloped having, apparently, afforded some 

 protection. The bones are coloured and strongly 

 impregnated with iron ; especially those in Brook 

 Bay, which are permeated throughout with py- 

 rites; groups of brilliant crystals of this mineral 

 often invest the outer surface. The medullary 

 cavities are occasionally found lined with white 

 calcareous spar, and the cancellated structure of 

 the bone is often filled with this substance.* 



The quantity of bones collected from the sea- 

 shore in Sandown, Brixton, Brook, and Compton 



• Some of these osseous boulders and pebbles afford interesting sections 

 for the microscope. Slices from specimens presented to me by the Rev. 

 Charles Pritchard, of Clapham Common, beautifully display the canci Uab d 

 structure ol thi bone, with the rolls lined with pyrites and calcareous •-par. 



