74 JR. M. Brydone — Further Notes on the Trimmingham Chalk. 



have been transported from any distance, as it would not have held 

 together, forms an interesting parallel to the masses of coarse shingle 

 which lie on the top of the northern part of the south bluff as 

 recorded in my previous pamphlet (see also Fig. 1 hereto). 



Another point of interest is the behaviour of the grey bed in the 

 seaward face of the bluff. As this was cut back the grey bed 

 developed a deep pocket, shown just beginning in Fig. 7 and 

 complete in Figs. 13 and 17, at the bottom of which the gritty basal 

 seam thickened considerably and became exceptionally coarse. 

 (It will be noticed in these figures that the two upper flint beds 

 shown in fig. 1 of my previous pamphlet have become comparatively 

 indistinct, while the third has become very marked. At the moment 

 of writing the second is regaining its importance.) On the left-hand 

 side of this pocket the base of the grey chalk rises very sharply, so 

 that the chalk which strings out into the clay, thin as it is, becomes, 

 as on the other side of the bluff, composed of a layer of 0. limata 

 chalk below and a layer of grey chalk above. There is clearly at 

 this point a very strongly marked unconformity between the two 

 beds of chalk. 



Another point is that 0. limata chalk has come in between the« 

 grey chalk and the clay in the cross section at the end of the north 

 side of the grey chalk bay and at several other points in this mass 

 where the grey chalk and clay were previously in contact, so that it 

 seems fair to assume that the distance by which the grey chalk 

 overlaps the 0. hinata chalk is slight everywhere. Whenever the 

 grey clialk has been removed from off the 0. hinata chalk beneath 

 it the latter has always presented a decidedly wave-worn and 

 smoothed appearance. 



This grey chalk, as before stated, presents some remarkable 

 peculiarities besides its basement bed of grit with flint and chalk 

 pebbles. It is very soft, but contains a great abundance of hardish 

 lumps of varying shades of grey which are not clearly rolled, but 

 have ver}'^ smooth and suspicious outlines. These lumps are very 

 similar in texture, and, so far as I know, identical in fossil contents 

 with their grey matrix. The flints present two facies. One, which 

 is generally small, is dark grey throughout and very soft, being 

 often little more than a central mass of spongy texture, but no 

 definite shaj)e, surrounded by a very thin skin, very imperfectly 

 silicified and easily cut with a knife on slight pressure. The other 

 type appears to be confined to the base of this chalk, and includes 

 nearly all the large flints. It is very thoroughly silicified and 

 black inside with little or no cortex, and light bluish grey outside. 

 These, like the included lumps, suggest gentle rolling, but contain 

 only the same fossils as those of the grey matrix, including the 

 peculiarly characteristic ones, and certainly no specimen of 0. limata, 

 which occurs in profusion in the flints of its own horizons. The 

 bed as a whole is certainly not reconstructed, for the grey matrix 

 abounds in fragile fossils in absolute perfection, the most striking 

 being Odrea iuceqiiicostata, bivalved Ostrea imgulata, and numerous 

 branches of Vincularia and other Polyzoa. The fossils show the 



