9iear Colchester^ Essex. 437 



Valvata pisciiialis appears to be the only species that has 

 escaped destruction. I have, it is true, detected forms of the 

 genus Planorbis in these beds; but, in trying carefully to 

 remove them, they have invariably fallen to powder. 



The beds containing these lacustrine shells, and other or- 

 ganic remains to be noticed, consist principally of white cal- 

 careous marl and ferruginous sand, mixed with broken shells, 

 and alternating for about 4 ft. in thickness; the whole sur- 

 mounted by what was formerly called a diluvium, 3 ft. thick, 

 consisting of brown clay, and gravel composed chiefly of 

 rounded and angular flints, quartz boulders, and bouldered 

 fragments of the trap rocks. These mineral substances, more 

 or less mixed with sand or clay, and coloured with oxide of 

 iron, constitute the surface of our neighbourhood : and are 

 the source from which the materials are supplied for our 

 excellent roads. 



Under the beds containing the shells and fragments is a 

 stratum of lignite 3 in. thick, which divides these beds from 

 a thick deposit of clay that lies beneath them; in this lignite 

 I have found shells of the Cyclas rivicola in groups from the 

 bed. Immediately above this lignite, and associated with the 

 shells and fragments, I obtained a horn of the ox, and some 

 large fragments of bone, and amongst them a scapula belong- 

 ing to the same animal. This horn, or rather part of a horn 

 (for both ends are truncated), measures 16 in. in circum- 

 ference at the larger extremity, and is 21 J in. in length, not 

 continuing to a point, but broken off to 2 in. in diameter at the 

 smaller end : some of the fragments appear to be parts of 

 the skull, and are very thick compared with the thickness of 

 the skull of our recent ox. These remains were found, in the 

 winter of 1832, in excavatinop for brick earth ; and I thouo^ht 

 myself very fortunate in rescuing from destruction such me- 

 morials of days long gone by. About a month ago, I also, 

 fortunately, obtained, from the same stratum and the same 

 spot, some more bones, with pieces of deer's horns, antlers, 

 &c., which at present form a part of my little collection. 



Under the layer of lignite is found a deposit of fine blue 

 clay, with mica regularly disseminated throughout it in very 

 small plates ; there is also much calcareous matter in it. This 

 is a most excellent material for white bricks, chimney-pots, 

 &c., for which it is extensively used. 



This clay is generally excavated to the depth of 8 ft., or 

 10 ft., from the layer of lignite mentioned above. At this 

 depth there are found many rounded portions of soft chalk, 

 the size of walnuts, and some smaller, although we have no 

 chalk formation nearer than Sudbury, w4iicli is fifteen miles 



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