TRIMMER ON SAND-GALLS IN THE NORFOLK CHALK. 313 



contains two Paramoudras, in their proper vertical position. The 

 third line (c, c) is more irregular, and some of its tabular masses 

 of flint lie horizontally, while others stand up vertically ; and a lit- 

 tle below this line, on the southern side, are some irregular lines 

 of gray clay, with a ferruginous tinge. Above the fourth line of 

 flints (d, d) to the west of the middle point of same side, a seam of 

 similar clay is continuous for several feet. 



On the eastern side, towards the north end, similar seams of 

 clay occur above the lowest line of flints (a, a), at intervals of from 

 6 inches to 2 feet in perpendicular height. They are rarely more 

 than 6 inches long, and an inch thick. Several seams also occur 

 about the middle of the same side, below the level of the third line 

 of flints (c, c). Irregular seams of clay and sand appear also 

 about the middle of the western side of the pit ; and these occa- 

 sionally expand into masses of sand, 6 inches long and 2 or 3 

 inches thick. The seams of clay dip, on the south side toward the 

 north, on the east side toward the east, and on the west side to- 

 ward the west. In the north-east corner of the pit, the recon- 

 structed chalk rises to the height of 12 feet above the level of the 

 lowest line of flints (a, a). 



Near the middle of the eastern side of the pit, at the depth of 

 about 5 feet below the surface of the reconstructed chalk, a layer 

 of crag shells occurs, about 10 feet long, dipping eastward. The 

 general thickness of this layer is from 1 to 3 inches ; but in one 

 part, for the length of 2 feet, it swells' out to the thickness of 1 

 foot ; and the shells are here mixed with sand and a few pebbles. 

 Among the shells, which are chiefly in large fragments, Mr. 

 Wigham recognized Astarte plena, Tellina obliqua, and Cyprina 

 islandica, the last shell being the most abundant.* I have before 

 stated that the pan which underlies the fluviatile deposit of Mun- 

 desley, and the bed which overlies the fluviatile deposit at Rimcton 

 Gap, agree as to the species of shells which they contain ; and it 

 becomes a question with which of these two beds the crag of 

 Crostwick was contemporaneous. 



So solid in appearance is the reconstructed chalk of this pit, 

 that, until I discovered the above described layer of crag shells, I 

 had no suspicion that it was any thing but solid chalk ; and even 

 now, when I am convinced that a large portion of the matter in 

 which this pit is excavated is chalk-rubble, I am unable to assign, 

 with any degree of precision, the limits between the reconstructed 

 and the solid chalk. The fragments of chalk in the rubble of 

 Crostwick do not exhibit the slightest appearance of attrition. 



As to the deposits above the reconstructed chalk, they rise to 

 the height of about 4 feet above the general level of the latter. 

 Of the Pan there are no distinct traces. The lower of these over- 

 lying deposits are more regularly stratified than the upper. 



* The entire skeleton of an elephant was found some years ago, as Mr. 

 Wigham informs me, in a pit of chalk-rubble in the neighhourhood of Crost- 

 wick ; and, as he believe?, in this very pit. In this part of Norfolk, " marl" is 

 the name which the farmers give in common hoth to chalk and to chalk-ruhble. 



