18r)4.] PRESTWICH AND BROWN FISHERTON DRIFT. 10.5 



surface consists of materials derived from the destruction chiefly of 

 the chalk, but in part also of the Tertiary strata, and of the Green- 

 sands ; for, with a large preponderance of flint- and chalk-rubble, 

 there are also found round flint-pebbles and masses of saccharoid 

 sandstone from the Woolwich and Reading series, which, there is 

 reason to believe, once extended over this area. This debris also 

 contains many fragments of chert and grit from the greensand, 

 probably from the neighbouring vale of Wardour ; whilst the finer 

 materials from these several deposits have formed, when well mixed 

 together, the calcareous loam called brick-earth*. The whole of 

 this drift is spread out without order or regular structure, without 

 regard to the specific gravity of the materials, and comparatively 

 without wear ; sometimes the light porous brick-earth, and at other 

 times the heavy flint-rubble is at the top of the mass, whilst it often 

 happens that heaps of the broken flints are entangled singly, or in 

 irregular layers in the midst of the brick-earth. This flint-rubble is 

 perfectly angular, and exhibits scarcely any traces of wear from 

 rolling. The only specimens, in fact, exhibiting any long-continued 

 wear are the flint-pebbles derived from the Tertiary beds, and the 

 older origin of which, as pebbles, admits of no doubt. The greater 

 part of the bones also are broken, and retain their sharp fractured 

 edges. The underlying shell-marl, on the contrary, is the result 

 probably of a perfectly quiet, local, and uninterrupted accumulation, 

 for the shells are of all ages of growth, generally perfectly uninjured, 

 and are imbedded apparently on the spot where they livedf . 



It is probable that the physical features of this district at the very 

 recent geological period when the two above-named large extinct 

 mammals J, associated with the Ox and Deer referred to species of 

 which the descendants are supposed still to exist, roamed over the 

 land, and the minute mollusks identical with recent species swarmed 

 on the surface of that land and in its waters, differed to no great 

 extent from those prevailing at the present day. The valleys are 

 possibly rather deeper, and may be a few feet higher above the sea- 

 level than they were at that period. — [J. P., Jun.] 



* I have not thought it necessary to repeat in each separate section the whole 

 of the rock-debris forming the beds of drift-gravel. The preponderating mass 

 merely is defined. Debris from these Tertiary and Cretaceous beds is found 

 scattered irregularly throughout the drift (and also in the surface-bed), but the 

 flint-rubble forms in all cases the distinguishing feature. In the bed beneath the 

 shell-bed at Mr. Harding's pit, specimens of these rocks are, however, scarcer ; 

 though in this bed Mr. Brown found a subangular fragment of limestone, appa- 

 rently from some of the secondary rocks of the vale of Wardour. 



t I purposely confine myself in this and the following two papers merely to a 

 statement of the probable conditions prevailing in the several localities at the 

 life-period of their respective faunas, reserving the more general theory, connected 

 with the extent and nature of the geological changes of the Pleistocene period, 

 until I shall have brought a greater number of facts, properly grouped, before the 

 Society. 



X From the character and age of the deposit, and from the numerous unde- 

 terminable fragments of bone which I have seen, I believe that the group of Mam- 

 mals will prove to be far larger than here described. It will be important to 

 collect further evidence on this subject. 



