758 MISS M. I. GAEDIXEE OX THE GEEENSAXD BED 



described, though there is always some in any slide of the heavier 

 minerals separated from this sand. It is in long narrow prisms and 

 grains. 



Tourmaline is present in about the same quantity. It is dark 

 brown, purplish grey or very light and almost colourless. The 

 light variety is in small and very perfect crystals, often as broad as 

 they are long, so that they have the outline of a hexagon. They 

 are terminated at both ends by the rhoml)ohedi'on-planes, but the 

 darker varieties are generally broken, or if not, the rhombohedral 

 planes are only at one end, and the basal plaue is developed at the 

 other. 



Anatase has been looked for, but not found. 



The description so far applies to specimens from all the places 

 mentioned except Sudbury, that is to say, since these places are 

 distributed along the whole length of the southern outcrop, it may 

 be taken as a general description of the basement sand of the 

 Thanet Sands in the South of England from a mineralogical point of 

 view. The following minerals occur in very small quantities, and 

 so are not in any way characteristic. 



Garnet. — A few minute colourless dodecahedra have been noticed. 

 One measured -02 millim. from one dodecahedron-face to the parallel 

 one. One has grown round a smaller red crystal of the same form — 

 a fact which seems to point to their being garnets. 



Aciinolite. — 'A few fragments of a fibrous-looking green mineral 

 strongly pleochroic, or yellow-green, with vibrations parallel to the 

 length, and blue-green with those in the opposite direction are 

 probably actinolite. 



Epidote. — One somewhat rounded crystal of the outline of an 

 oblique parallelogram with the corners rounded off, strongly 

 pleochroic and with very distinct cleavages, has been referred 

 for me by Mr. Davies to this mineral. Judging by the colour and 

 pleochroism other grains may be of the same mineral. 



Chalcedony. — There are a few grains of a mineral polarizing 

 in grey and having a spherulitic structure. Such grains are common 

 in the residue of chalk dissolved in hydrochloric acid. 



Organic Remains. — A few microscopic organisms have been met 

 with, and are sufficiently numerous to render it probable that with 

 careful searching many genera might be found. The commonest 

 are siliceous, s]3herical bodies with a pitted surface, with a more or 

 less distinct dark centre, apparently not casts. These may be 

 either Eadiolarians or Diatoms. Casts of Foraminifera, probably of 

 the genera Planorhulina and Textularia in a clear, colourless 

 mineral, perhaps chalcedony, have been noticed. 



The Greensand hed at Sudbury. — This bed has apparently been 

 classified with the Thanet Sand on account of its position and 

 colour. The great point of difference from the southern greensand 

 already described is in the much larger glauconite-percentage, which 

 gives the bed a greener, less grey colour. Glauconite constitutes about 

 75 per cent, of the grains, and the proportion by bulk is still greater, 

 since the glauconite grains are larger and the other grains smaller 



