TRANSACTIONS OP THE SECTIONS. 133 



mmiites vertebralis, A. hijdex, A. perarmatus, A. Henrici, A. catialicuUdus, A, Go- 

 liathus, Belemnites tornatUis, B. hadatm ; the ouly described gasteropod, Pleuroto- 

 viaria reticulata. Bivalves : rectenjihrosiis, P. lens, P. viminem, Gryphcca dilatata, 

 Lima j)ectiniformis, Avicida c.rpatisa, A. ovalis, A. elliptica, Trif/o»ia costuta, T. cla- 

 vellata, Astarte uvata, A. hiricla, &.c. Mauy new species were noticed ; among others, 

 Gryphcea ehngata, Avicula pterosphena, Pkurotoinaria amphicelia, Liitorina peror- 

 nata, &c. 



On some Phenomena connected ivith the Drifts of the Severn, Avon, Wye, ami 

 Usl: B>j the Eev. W. S. SYMO^'DS, F.G.S. 



Alluvial Deposits. — The first point we remark is the gi-eat difference which at 

 present occurs in the deposition of silt and alliiviiim by such rivers as the Severn 

 and Avon, compared with swift-flowing streams like the Wye and Usk, which have 

 a fall of as much as 2^ feet in a mile along their general coiu-se. In some localities 

 the Wye has shifted its course, filled up its former channel, and cut out a new bed, 

 within' the memory of man, as proved by an old map, which gives the position of 

 the celebrated Ross Oak, now knowTi as the "Burnt Oak," and the river aa it 

 flowed a centiu-y and a half ago. A broad surface of meadow-land now sweeps 

 where the Wye then flowed, and the river now runs some 70 or 80 yards from the 

 former bank on which that old oak stood. This is not the case with respect to the 

 smoothly flo-wing Severn and sluggish Avon to anything like the same extent. 



The point, however, to which the author woidd direct attention is, that all these 

 rivers may and do alter theu" courses, and destroy and re-form their alluvia over and 

 over again, for age after age, ■\%-ithout in the slightest degi-ee changing their courses, 

 save as regards the level alluvial land. 



Tlie Lake Period. — It is well known that there was a time, antecedent to the 

 present configuration of land and river sm-face, when the Severn, Avon, and Wj-e 

 flowed, as the river Shannon does now, through a chain of lakes of various sizes, 

 and which lakes are now silted up and fomi the celebrated " holmes " or river- 

 meadows. The author formerly inferred that the relics of the gTcat quadrupeds 

 found so abundantly on the banks of the Avon, at Bricklehampton and Cropthorne, 

 at Kempsey and other localities on the Severn, were disinterred from banks of mud, 

 silt, and gravel, which were formed on the shores of the ancient lakes. It is here 

 that he woidd coiTect the inferences that might be drawn from any correlation of 

 these di'ifts, which contain the remains of the hippopotamus, rhinoceros, elephant, 

 cave-hyfena, and extinct oxen and deer, with the deposits of the Lahe-epoch. They 

 belong to a distinct qwch, and ofter a distinct history. 



Low-level Drift. — Mv. Prestwich has sho^^-n that certain drifts and gi'avel 

 beds above the Avon, Severn, and other rivers, which ho designates as "low-level 

 drifts," are altogether antecedent to, and independent of, the detritus which fills 

 up the beds of the fonner lakes. They belong to a distinct epoch, and represent an 

 entirelj' diflerent water surface. Instead of dipping under or into the lacustiine 

 deposits, in many localities they dip away fi'om the old lake silts, and are slightly 

 upheaved. They are, in fact, the relics of broad and, probably, rapid rivers, of which 

 the fonner channel must have been 30 or 40 feet above the level of the silted-up 

 lakes. 



The period of the " low-level drift " was, then, anterior to that of the Lake epoch 

 in this pai't of England ; and it is in these beds, and not in the lacustrine drifts of 

 Worcestershii-e, that the explorer finds such numerous relics of the extinct mam- 

 malia. 



These beds are well developed near the Avon at Bricklehampton and Cropthorne, 

 and near the Severn at Upton-on-Severn, and near the Ox-eye Gate, about a mUe 

 from Tewkesbury, on the Ledbury high road. Near Worcester they may be seen 

 in various localities ranging above the margins of the former lakes. These drifts 

 are also well developed on the banks of the Wye, near Hereford, as at Broomy 

 Hill and the Infirmary. At Brecon, ^Ir. S3monds found a most interesting old 

 river-margin of well-stratified sand with rolled pebbles, on the slope of a hill, and 

 at a height of 50 or 60 feet above the liver Usk. 



High-level Drift. — Certain gi-avels and drifts are foimd at a tnuch higher level 

 above the river-courses than the drifts just alluded to. These gravel-beds cap the 



